THE

GEOLOGICAL MAGAZINE.

NEW SERIES.

DECADE IV. VOL. I. JAN UAKY DECEMBER 189 4.

THE

^ GEOLOGICAL MAGAZINE:

OS,

WITH WHICH IS INCOEPOttATKD

THE G-EOLOG-IST."

NOS. CCCLV. TO CCCLXVI.

EDITED BT

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OF TKE BEITISH MUSEUM OF NATURAL HISTORY; VICE-PRESIDENT OF THE PAL^ONTOGRAPHICAL SOCIETY,

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NEA?^ SERIES. 33EC^33E JTV-. VOX.. I. JANUAEY— DECEMBEE, 1894.

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LIST OF PLATES.

PLATB TO FACE PAGE

I. Prolecanites compressus, J. Sby., sp H

II. Diagrams illustrating the structure of tlie Dolomites 49

III. Map of a portion of the Dolomite Area 49

IV. Lower Palaeozoic Fossils from Yorkshire 108

V. Sections of Lithothamnion and Solenopora 145

VI. Eestoration of Camptosaurus dispar, Marsh 193

VII. New Bala Trilobites 241

VIII. Appendages of Triarthrus Becki, etc 246

IX. Fossil Phyllopoda 289

X. Restoration of Elotherium crassum, Marsh 294

XI. Footprints from Kansas Coal-measures 337

XII. "Western Australian Cephalopoda 385

XIII 433

XIV. Carboniferous Trilobites 481

XV. Cyclus: Carboniferous 530

XVI. Portrait of WiHiam Topley, F.R.S 570

LIST OF WOODCUTS.

PAGE

Six Figures illustrating the Glaciation of Switzerland 35

Overthrust plane at Sasso Pitschi, Dolomites

Jurassic Bryozoa

Tooth of Oxyrhina crassa, Ag '^

Old Delta near Eidfjord 9*

Diagrammatic Eeconstruction of Dartmoor

Figures of Crystals containing Inclusions of "Water and Gas , 102

103

Augen-gneiss, sections along the " dip-plane" H^

Remains of Crystals in crushed Augen-gneiss 115

Gneiss with "rucking" !■'■'

Vein of streaky and banded granite intrusion in green-schist 119

Slab with Bryograptus ramosus, Brogger 1"0

First chamber of Orthoceras, with protoconch attached 142

Longitudinal section of Solenopora compacta, BiUings, sp 147

Tangential ,, » »> >> ^^"^

,, nigra, Brown, sp. . 149

Longitudinal ,, ,, ,, jiirassica, Mch 150

Tangential ,, ,, 151

Section through a part of St. Gothard Tunnel 154

Micaceous gneiss with Sand-grains from St. Gothard Tunnel 155

Quartz-grains in Micaceous gneiss 156

Felspar-grains in Micaceous gneiss 158

Section of Cordierite Crystal in metamorphosed Skiddaw Slates 169

Longitudinal Section of Solenopora Jiliformis, Nich 195

Tangential Section of Solenopora dendriformis, Brown 196

Longitudinal Section of Hthothamnion foecundum 197

Part of roof of conceptacle of Lithothamnion fcecundiim decalcified. . . . 198

Longitudinal Section of apical shoot of Corallina Mediterranea 198

Longitudinal Section of thallus of Amphiroa exilis 199

Surface view of the thallus of Melobesia deformans 199

viii List of Woodcuts.

PAGE

Cells of Lithothamnion, etc 201

A Specimen of Pigotite from Cornwall 224

Section of the Eastern side of the Platberg 290

Ornament on the valve of Elymocaris Sindei 292

Temnocheilus coronatus, M'Coy . . . ,. 296

Coast Section at Saltern Cove 367

Eailway Section at Kimberley, Notts 367

Map of the North -"West Territories of Canada 396

Section of Euhble-drift, Portland . . . .' 432

Aptychus in Ammonites 455

Section of Aptychus Icevis, von Meyer 457

458

Vertical Section on the Banks of the Hodder 484

Pygidium of Fhillipsia Derbiensis, Martin 488

,, ,, gemmulifera, Phillips, sp 488

Map of Church Beck, Coniston 490

Map of the Tumuri Valley 500

Longitudinal Section through the Canon of the Yumuri ....... 501

Section across the end of the Tumuri Valley 501

Erect Stem of Sigillaria, Coal-measures, Rochdale 528

Cyclus Woodwardi, Reed 531

,, testudo, Peach 534

;8'co«i, H. "Woodw. 537

Diagram of the River Lowther 540

,, Map of Mosedale and Wet Sleddale 541

Sand-blast Apparatus for developing fossils " 654

Enlarged section of part of Sand-blast Apparatus 555

THE

GEOLOGICAL MAGAZINE

NEW SERIES. DECADE IV. VOL. I.

Ho. I.— JANUAEY, 1894.

o:n,x(3rXi<rj^Xj j^i^tigles.

I. Coral in the " Dolomites " of South Tyrol.

By Miss Maria M. Ogilvie, D.Sc. (Lond.).

(Part I.)

I. General Character of the Scenery The Interpretation of the

Mid-Triassic Succession given by the "Coral Reef Theory."

AT the meeting of the British Association in Nottingham, in August of last year, a joint discussion on "Coral Keefs " was held by the sections of Zoology and Geology.^ Prof. SoUas, in opening the discussion, referred to the "Dolomites of South Tyrol " as a country affording brilliant examples of Fossil Coral Eeefs. He demonstrated this by sections taken from the well- known work of Mojsisovics, and showed several photographs of some of the more imposing dolomite mountains Schlern, Langkofl, and Sella which had been explained as reefs of Triassic age. In the course of the discussion. Dr. Hickson said he believed there were no corals in these so-called fossil reefs. Dr. Eotbpletz cor- rected this statement, saying briefly that there were corals in the dolomite and limestone rock, along with other groups of marine animals, but that many of the sections shown by Prof. Sollas were incorrect. Prof. Bonney emphasized the ample evidence of Coral life in many parts of the district which he had visited.

I may be pardoned for recapitulating the part of the discussion bearing on South Tyrol, as I wish to state here the conclusions which I have formed with ^regard to Coral Reefs from my geological work in that neighbourhood. So far as South Tyrol gives countenance to one theory of the growth of Coral Eeefs or the other, it supports in the main Murray's theory and not Darwin's. It displays striking analogies with the observations of recent reefs made by Agassiz in the West Indian and Caribbean Seas, by Dr. Guppy in the Solomon Islands, by Dr. Murray on the Barrier Eeef of Tahiti and the Great Ghagos Bank, by Prof. Semper in the Pelew Islands, by Dr. Eein, Dr. Sydney Hickson, and others. Some of the special points of correspondence may be indicated at once. Volcanic eminences formed submarine platforms in the Triassic ocean of South Tyrol, on which Corals built in Wengen and Cassian time. One special

1 An account of the discussion is given in "Nature," October 12th, 1893.

DECADE IV. VOL. I. >0. 1. 1

2 Miss M. M. Ogilvie— Coral in the ''Dolomites:'

ridge, south of Groden and Enneberg, apparently the outer- most at that time, formed the basis for a more or less continuous barrier-like chain of reefs, behind which (i.e. to the north) deposits collected of a different nature from the ordinary marine deposit of the Southern Ocean. These deposits include in their uppermost horizons the wonderful Cassian fauna of Enneberg, and probably the faunal conditions of the Cassian-Enneberg sea of Triassic South Tyrol may be justly compared with these of the Caribbean Sea at the present day. At a later Triassic period, in Kaibl time, banks of reef-coral were formed on raised beds of ordinary submarine deposit. On the other hand there is every reason to suppose that in the par- ticular periods of Trias in South Tyrol pre-eminent for the growth of Coral Eeefs, the sea-floor was undergoing extensive movements of subsidence, subject to oscillation in the near vicinity of volcanic action. In the St. Cassian area, between the two main periods of Coral gi'owth an interval of quiet subsidence intervened, marked in many places by the cessation of Coral growth and the accumulation of a marine deposit enclosing calcareous algge.'

The Wengen and Cassian Coral Reefs of Groden, Enneberg, and Upper Fassa have remained, with biit rare exceptions, limestone. The actual thickness attained by the individual lenticular Coral Reefs or the Coral Banks is in no case very great, seldom more than 150 feet, and usually much less. The steep slope of the outer chain of reefs was mainly composed of volcanic rock with interbedded reef-limestones. As negative evidence it may be mentioned that the so-called "Dolomite Reefs," viz. the thick dolomite massifs of Schlern, Sella, etc., have originated as marine deposits and not Coral Reefs, probably calcareous in the greater part of their thickness, and only in their upper horizons originally dolomitic. The reef-like appearance assumed by these dolomite massifs is in small measure due to the variation in the character of contemporaneous Triassic deposits, but it is chiefly the result of the movements of the rocks in Tertiary time.

I have selected for the sketch-map^ a long stretch of country between the Eisack Valley, with the Brenner railway on the west, and the Ampezzo Valley on the east. The map displays at a glance the characteristic physical features. Precipitous rocks, generally of a creamy or rose-tinted crystalline dolomite, rise to great heights above green swelling passes and grazing land, or sometimes descend at once into deep gorge-like vallej's. The artistic sense scarcely knows which to love most the romantic region of fir-wood and stream and human habitation, or the wild solitariness of the rocks beyond. Villages are perched midway between mountain and ravine, looking in some of the narrower valleys as if a push would throw them into the gap below. The simple Ladinian folk wander

^ Mr. George Murray made the following observation in the Antilles: "Many- coralline sea-weeds living at greater depths than the Corals grow with a stout incrustation of carbonate of lime, and thus form great masses which seem to nearly rival the true Coral Eeefs in bulk " (" Nature Notes," February, 1891).

2 The Map will appear in the February Number with Part II. of this paper.

Miss M. M. Ogilvie— Coral id the ''Dolomites:' 3

summer and winter among the rough winding paths and dilapidated huts, content to lead their cows and mow their hay. In the wider valleys the sun ripens hearty crops twice a year, and life flows on pleasantly, after a lazy Italian fashion. The barrenness of the dolomite mountain is such that even chamois rarely frequent their clefts and terraced table-lands ; snow caps most of them during nine months out of the twelve, and is perpetual on the highest summits.

With the exception of a few scattered remnants of Jurassic and Cretaceous rock, the geological age of the deposits exposed through- out this country is Triassic. We are concerned with the history of Triassic deposit in South Tyrol, in the midst of which, we are told, there came a long epoch of Coral growth and reef-building. If this be true, the data of the geologist have a keen interest both for the geographer and the zoologist, whose duty it is to compare these fossil Coral Reefs with reefs now growing, and find corroboration or the reverse for the various theories which have been advanced regarding the growth of recent Coral Reefs. The chief data which geology determines, are the exact nature of the sedimentary rocks, the order in which they succeed one another, the fossil remains which they contain, and any particulars regarding the manner of occurrence of the fossils. That seems a simple enough commission, and yet in practice it is often very hai'd to execute, no part of it more hard in the Alps than that of determining the order in which the I'ocks succeed one another. For the sediments which were deposited by the great basins of water in Triassic time have since been folded and twisted and raised into entirely new positions in relation to one another. So that a rock which was once below is now alongside or even above its neighbour or its fossils have been destroyed, or a volcanic invasion has taken place ; in fact, endless accidents may have happened since Triassic time, and it requires much time and patience to unravel the mysteries introduced into a once simple succession. In a word, to be a good ancient geographer of the Trias, one must first be a wary stratigraphist.

We shall begin by quoting the succession of Triassic rocks in South Tyrol and the interpretation of it given by Mojsisovics ^ :

Eh^tic Beds. Dachstein dolomite. Raibl marls, sandstones, dolomite. Coral f ^''^^^i'^'^ Dolomite"! thinning into TCassian marls and limestones, j^j, -^ Wengen ,, I contemp. 4 TVengen shales and volcanic ash.

[Buchenstein ,, j deposits of (^Buchenstein limestones and ashy rocks. Muschelkalk (Alpine) limestone or dolomite. "Werfen shales and thin bedded sandy limestones. Permian Bock:. The actual part which these rocks take in the landscape may be briefly described. The so-called " Coral Reefs " rise as sheer precipices 2000-8000 feet high, or dwindle to nothing. The gaunt form of their cliffs is unbroken by familiar planes of bedding. Eaibl marls draw themselves as a narrow band above them, and

"■ E. Mojsisovics v. Mojsvar, "Die Dolomit-Biffe von Siid Tirol und Venetien," Wien, 1879.

4 Miss M. M. Ogilvie Coral in the "Dolomites."

Dachstein dolomite, well stratified and often of very great thickness, builds the highest terraces and precipices. The Cassian, Wengen and Buchenstein sedimentary beds are exposed on the passes between " reefs," on their lower slopes, and over the large meadows which the people of the place call" Alpen." The Muschelkalk and Werfen series form the bed of the streams in the rapidly descend- ing mountain valleys. It may be at once remarked that typical fossils have been found in all members of the succession. In the "reef-dolomite" fossil remains are extremely poor and scanty; plant algae are got even more often than Corals, Gasteropods, or Bivalves. Ammonites occur, but usually in too meagre a state of preservation to be of much service in identifying the age of the rock.

Besides the layers of volcanic ash and lava which are interbedded with the Wengen beds, there is every here and there a massive looking volcanic rock, Augite Porphyry, which surprises the eye by its strong contrast to the doloraitic rocks. Everyone knows that Coral growth in our present seas is particularly luxuriant where volcanic action is occasionally felt, and this seems a strong argument in favour of the view which explains these Triassic dolomites as Coral limestones, largely magnesic, which were built in a volcanic sea of the far-away Trias period. The later conversion of such magnesic limestone reefs into pure dolomite also finds its parallel in recent reefs. So that the " Coral Eeef Theory of the Dolomites " presents, as a theory, no problem which is not in harmony with recognized facts, unless we except the enormous thickness attained by the reefs, and the occurrence on their upper surfaces and slopes of an appearance which Mojsisovics observed and called " overcast bedding."

A geological theory, however, stands by virtue, not of its probability argued from Nature's Present, but its absolute fitness to the facts observed in Nature's Past. And, when the same facts may bear two or even more explanations, the theory which is to stand in Science must fight for its position as the fittest survivor ! "We have to ask ourselves if the Coral Reef theory offers the only probable explanation of the dolomite cliffs. The mere occurrence of a couple of thousand feet of limestone or dolomite is part of the A B C of Geology, when taken as the accumulation of ordinary marine deposit. Dachstein dolomite is such a rock, and it still carries testimony of its origin in the numerous Megalodon bivalves and other fossils which it contains. Again, a considerable amount of variation in the thickness of any marine deposit might be expected, especially where volcanic eruption had previously disturbed the sea- floor and produced all degrees of inequalities by heaping up its ashy flows in some parts more than in others. But the special difficulty said to meet us in the case of the Cassian and Wengen dolomite of South Tyrol is, that rocks of 2000 feet in thickness rise quite suddenly from the midst of sedimentary earthy beds, and show certain curious appearances in relation to them. The dolomite rock seems to dovetail at its extremities into the marly and ashy beds,

Miss M. M. Ogilvie Coml iri the "Dolomites." 5

giving rise to strange anomalies in the geological succession, which could only be explained by regarding every case as one of con- temporaneous deposition of different classes of rock very close to one another, so-called " Heteropism." Such difficulties can only be solved by stratigraphy, and to that we must turn for proof of the data on which the Coral Reef theory rests.

For the sake of clearness in writing, we prefer to use, instead of the triple term applied to the reef-dolomito by Mojsisovics, the single name given by von Richthofen, of " Schlern dolomite," ' from its characteristic occurrence at Schlern Mountain, south of the Groden Valley.

II. Normal Marine Formations of Mid-Trias in the Southern Alps Submarine Volcanic Action in Upper Fassa and the neighboui'ing districts The "Dolomite Reefs" of Enneberg and Ampezzo correspond to part of the Normal Marine Deposits of the South.

Whereas during the Wengen and Cassian period, volcanic activity was rife in the northern part of the area covered by the sketch-map, an accumulation of marine deposit appai'ently went on during a steady subsidence of the sea-floor over the southern areas. Great thicknesses of limestone and dolomite represent this period in the southern part of the South Tyrol, and in the Venetian and Berga- masker Alps. These are known in different localities as Esino limestone, Marmolata limestone, Schlern dolomite. The fauna is liable to great variation, but includes for the most part a typical assemblage of Mollusca, Eohinoderms, Corals, and Gyroporellas (sea algae). This we may regard as the normal oceanic formation of the mid-Triassic period in the Southern Alps.

In the Upper Fassa and Groden, Enneberg and Ampezzo districts, intermittent outpourings of volcanic matter took place from one or more submarine craters, associated perhaps with the proximity of this part of the sea to pre-Triassic land of Paleozoic and crystalline rocks, and with Triassic earth-movement. Be that as it may, the southern rocks of Schlern dolomite, Marmolata and Esino limestones, were clearly collected in deeper waters than the contemporaneous deposits immediately to the north. This is nowhere better seen than at Schlern Mountain, where the deep-sea deposits on the south side of Schlern pass rapidly into the volcanic lavas and shallow-water deposits, on the Seisser Alpe to the north. According to von Richthofen's original interpretation of this district, the upper part of the " Schlern dolomite " of Schlern was younger than any of the sedimentary beds on the Seisser Alpe, a stratigraphical fact of general import, which many geologists have since verified at this point.

Following an irregular line eastward and south-eastward, we may trace the same occurrence of stratigraphical facies. It takes place most suddenly where the Wengen lavas are thickest, i.e. in Upper Fassa. The dovetailing of the dolomitic and calcareous

1 Sclilem Dolomite. Vide von Eichthofen, " Geognostisclie Beschreibung der Umgegend vou Predazzo, St. Cassian und der Seisser Alpe," 1860.

6 Miss M. M. Ogikie Coral in the "Dolomites/'

strata with volcauic and marly beds whicli takes place along this volcanic zone is therefore perfectly comprehensible in the light of every-day facts of deposition. There is no need to call the massifs of Scblern, Eosengarten, Latemar, Marmolata, etc., " Coral Reefs," merely because a thin line of heteropic division may be ti'aced between these two areas of Triassic rock in South Tyrol. More- over, the local recurrence of volcanic activity during a prolonged period would explain the continuance of different conditions in adjoining districts. While a simple interpretation such as the above would explain one of the main features of Triassic geology in South Tyrol, it may be objected that it would not apply within the volcanic district itself, for it is in Enneberg and Groden, more than in any other part of South Tyrol, that the curious suddenness of the " Eeefs " strikes the eye.

As I have said in a previous paper,^ every member of the Triassic succession in South Tyrol presents variations in its thickness when followed from place to place. More especially is this true of the beds from Muschelkalk to Dachstein Dolomite. The names Cassian, Wengen, and Buchenstein mark different horizons in a series of volcanic lavas, ashy and tufaceous marls, calcareous marls and lime- stones, which may, lithologically considered, be united as one series. This series represents, no doubt, the upward continuation of Alpine Muschelkalk much as the Partnach beds do in North Tyrol. ^ Zones may be followed in which certain fossil genera predominate in the number of individuals and species ; but the palaeontological facts give us not so much a clear succession of types as an index to the facial conditions which influenced the life of the period.

For instance, Halohia Lommeli is a fossil bivalve which is common in tufaceous beds both of Buchenstein and Wengen age ; but in Buchenstein limestones the general character of the fauna is more like that of the Muschelkalk, whereas limestones of the Wengen age contain the remains of Corals and Echinoids like those in the next following Cassian deposits. Again, Posidonomya Wengensis is another bivalve which gradually outnumbers Halohia Lommeli in tufaceous beds belonging to upper horizons of Wengen beds, and it is a fossil which again and again reappears in Cassian time always associated with the same lithological character of deposit, and shewing but slight varietal changes in its outward form. It is one of these persistent types which saw the birth and destruction of innumerable shoals of less fortunate species and genera characteristic of the Cassian limestones.

In the district of Upper Fassa there are true Augite Porphyry lavas of Lower Wengen age, which appear more or less inter- stratified with grits and tuffs. In the Enneberg districts, i.e. north of Upi^er Fassa, the lavas pass into black earthy tuffs and crumbling grits, in which the fauna is very limited and fragments

1 " Contributions to the Geology of the Wengen and Cassian Strata in South Tyrol," by M. M. Ogilvie," Quart. Journ. Geol. Soc, vol. xlis. p. 47, February, 1893.

2 "Ueber die Entwicklung u. Verbreitung der Partnachschichten," etc., by Dr. T. Skuphos, Jahrb. der k.k. Geol. Eeichsanstalt, 1893, Ed. 43, p. 178.

Miss M. M. Ogilvie Coral in the " Dolomites. ^^ 7

of plants are of frequent occurrence. Mojsisovics has proved that these invasions came from a submarine volcano, probably in Upper Fassa, w^hich " lay on the edge of the district of greater subsidence " to the south. " In Triassic time, as we are taught by the history of the Triassic reef masses, a certain protraction took l^lace in the subsidence going on at the edge of the insular core of older rocks to the north as compared with a more rapid subsidence of the outer regions " (Mojsisovics, " Die Dolomit-Riffe von Siid- Tirol und Venetien," p. 525). We may naturally suppose that Augite Porphyry lavas foi'med irregular ridges on the disturbed sea-floor, more especially near the eruptive centre. From the beginning of this period we trace a marked diiference in the deposits and fossil remains of the non-volcanic and volcanic areas respectively south and north of the Upper Fassa ridge, and even considerable variation within the shallow volcanic sea itself. A representation of the sea-floor in this period is given in Diagram I.

Corals found abundant " coigns of vantage " and were aided by Echinodermata to form communities of organic life, often prevented from farther growth by new volcanic invasions, but ever and auon settling down afresh. The remains of these form the "Cipit blocks " and " Cipit limestones," which were first observed by von Eichthofen amid Cassian marls on the slopes below Schlern. Mojsisovics recog- nized similar limestones appearing intermittently over the whole area eastward. I have given special attention to the relations of these limestones with the contemporaneous rocks, and shall at once describe the more interesting results.

They, and not the mountains of Schlern dolomite, deserve the name of " Coral Eeefs " in South Tyrol. They never attain any great thickness ; generally in highly volcanic periods they formed mere isolated blocks composed of colonies of Corals and Echinoderms, and closely wedged amongst tuify marls. In less volcanic periods continuous beds spread over a larger area sometimes suddenly swelling out in lenticular fashion, sometimes perceptibly thinning into deposits full of other classes of animals. Stratigraphically considered, they occur as the equivalents of Cassian and Wengen strata, and in a less degree of Schlern dolomite and Eaibl strata, and they follow certain fairly definite laws of distribution. Diagrams I. II. and III. represent successive stages in the history of the heteropic deposition in South Tyrol during this part of the Triassic era ; Diagram IV. represents approximately the occurrence of Cipit Limestones in the contemporaneous series of rocks. In the Upper Fassa and Schlern districts the Cipit or reef-limestones occur at various horizons in the midst of volcanic earthy Wengen beds, or associated with sedimentary beds containing Halohia Lommeli, Posidonomya Wengensis, etc. They continue upwards in that district to the base of the Schlern dolomite, but are associated, north of the Schlern Mountain, in their higher horizons with characteristic Cassian fossils.

In Groden Joch and in Enneberg, the Cipit Limestones do not make their appearance until the Wengen beds are giving place to

8 Miss M. M. Ogilvie— Coral in the ''Dolomites:''

Cassian. The block-like structure observed in tbe Schlern and Fassa district becomes less prominent in Enneberg, and we are rather presented with thick unevenly bedded limestones full of Cidaris spines and Thecosmilian Corals, more rarely with Brachio- pods and small Mollusca.

These are immediately succeeded in Enneberg by the great mass of thinly-bedded typical Cassian beds. The latter, therefore, correspond on Stuores meadows to the upper part of the Cipit Limestones of the Seisser Alpe and Sella Joch, and to. some part of the lower horizons of Schlern dolomite at Schlern, and at Sella and Sasso Pitschi. Sometimes the outpouring of volcanic material, which was constantly recurring in Upper Fassa, caused the sudden disappearance of the rich fauna of Enneberg. During the short periods of disturbed deposition which then ensued, Echinodermata, even more than Corals, peopled the seas.

Thin beds of Limestone were thus formed at intervals amid tufaceous sediments of Cassian age, but the main thickness of Cassian beds in Enneberg is composed of soft marls and limestones full of the remains of Brachiopods, Mollusca, and many species of non-reef-building Corals. This fauna lived, I believe, in an inner area of quiet water, secluded from the Southern Ocean by the Cipit reefs and volcanic rocks, some deeper channels being left free.

Whereas the Wengen and Cassian beds retain their tufaceous character, in greater or less degree, throughout the whole district of Enneberg, they show it much less in the corresponding deposits of Ampezzo. Fine, unfossiliferous shales and clays take the place of the tufaceous grits, and although Corals and Sponges occur in hard limestones of Cassian age, they are seldom in suflScient magni- tude to form any appreciable reef-like thickening. The same is true of the northern or " Abtey " part of Enneberg, and of the deposits of Seeland Valley and Misurina, north-east of Ampezzo. Hence Cipit-Limestone building flourished most in the volcanic areas of Groden and Upper Fassa. I observed, however, in the higher horizons of Cassian strata at Ampezzo thick, reef-life extensions of Limestones, mostly one mass of the spines of Cidaris Hausmanni. They form bands of rock between softer beds, and are present as well in the undisturbed series below the Schlern dolomite of Lagazuoi as in the disturbed succession near the small Lago Majorera to the east (close to the Falzarego road). The stratigraphical facts afford evidence that the Cassian marls are both in Enneberg and Ampezzo succeeded by a dolomitic rock, and never conformably by fossiliferous Kaibl sandstones and marls. As might be expected from the occurrence of an upper palseontological zone of Cassian beds in the Ampezzo districts (Upper Cassian vide M. M. Ogilvie, loc. cit. pp. 46, 47), the dolomite rock which succeeds Cassian strata did not everywhere begin to be deposited at the same time.

In the south-west, where a true marine formation had been con- tinued throughout the Wengen and Cassian period, the deposit has only sometimes a stratified appearance. Mojsisovics has ascribed

Miss M. M. Ogilvie— Coral in ihe "Dolomites." 9

some parts of the Latemar and the mountains still further west to a lagoon formation ; but he describes a large, originally continuous, dolomite mass, " with the Schlern for the most northerly, and the Piz, near Sagron, for the most southerly point," as an immense Eeef. The Marmolata Mountain and the Mount Alto de Pelsa " are two important continuations of this mass, jutting out in peninsular fashion into the eastern district" {vide "Horizontal Extension of the Dolomite Reefs in Lower Wengen Time," Mojsisovics, loc. cit. p. 482). In the case of Schlern, where the upper part of this rock is stratified and the lower apparently unstratified, we are told that the lower part is Coral Reef, the upper part is lagoon deposit. But in many portions of this western " Reef," it has been proved that the remains of algje and mollusca form the important part of the deposit. Whether stratified or unstratified, there is no reason why the Schlern dolomite of this Western "Reef" should not be regarded throughout simply as a lagoon and marine formation. In no single case has it been proved that reef-coral continuously built vertical cliffs of Coral rock during the mid-Triassic period of subsidence represented by Esino limestone, Schlern dolomite, etc.

This typical calcareous or dolomitio rock in the south-west of the district succeeds in the northern and eastern areas, in greater or smaller thickness, the volcanic series and the marls and limestones of Wengen and Cassian age, gradually succeeding the upper horizons of the series towards Enneberg and Ampezzo. The so-called Schlern dolomite "Reefs" of these areas can never be said to be contem- poraneous with the marls at their own base unless, as in the case of the Schlern Mountain, denudation has allowed the rock to remain standing over such an extensive area that the dolomite of one portion is contemporaneous with the marls underlying the dolomite further north. To express the same fact somewhat differently, the fossil- iferous marls and limestones of Enneberg were not laid down against Coral cliffs, but form a deposit belonging to a definite palaeontological horizon, and succeeded by a dolomitic or calcareous rock of marine or lagoon formation. For this dolomitic or calcareous rock between the fossiliferous deposits of ascertained Cassian and Raibl age in the Enneberg and Groden district, it is best to preserve the name of Schlern dolomite,^ as no snfiScient faunal distinction has yet been carried out between different horizons of the said dolomitic rock in the south-western area of its complete development.

I must refer the reader to my sections and maps already published for further proofs of the conformable succession of Schlern dolomite on the Cassian beds in Enneberg. I shall now recapitulate the main conclusions which may, I think, be drawn from what I have already stated :

1. The frequent occurrence of Coral remains in the "dolomite" country is a fact, often repeated, but somewhat vaguely applied, bearing with it no evidence whatever of the Coralline origin of the " dolomites " themselves.

^ Schlern dolomite : In using the expression " dolomitic or calcareous rock '_' I "wish to take nothing for granted as regards the original or subsequent dolomitization of the rock. This question is outside the immediate interests of the paper.

10 Miss M. M. Ogilvie Coral m the '' Dolomites.'"

2. The Coral remains occur sometimes in isolated blocks, sometimes in large clumps of rock perforated by Thecosmilia species of Coral, and often full of fragments of Echinoderms. These blocks or clumps occur in the midst of fine volcanic mud, or the calcareous and dolomitic matter of the contemporaneous marine sediment, and form more or less continuous beds with lenticular reef-like expansions. The name they go by is " Cipit Limestones,''^ and they vary from 10 feet to 150 feet in. thickness.

3. "Cipit Limestones" are of episodal occurrence throughout the mid-Triassic era, appearing at entirely irregular horizons of all Triassic strata between the Muschelkalk and Dachstein dolomite. At the same time, in the ai-ea under dis- cussion, there is one horizon pre-eminent for the interbedding of Cipit Limestones, that is, the Cassian.

4. In its lithological character and faunal distribution, the "Wengen and Cassian period shows marked heteropism. While in deeper seas algse grew and Mollusca prevailed, there was, not far from the island coasts of the mid-Alpine core of rocks, a zone of submarine volcanic eruptiim. Lavas and ashes were swept intermittently over the sea-floor. Along the hem of this volcanic girdle communities of Corals and Echinoderms settled and formed a series of small barrier reefs (Cipit Limestones), frequently interrupted in their growth by fresh lavas. On the outer, seaward side, marine deposits continued to increase in thickness over a sinking basin ; on its inner side, at first only a few mud-loving species of Halobia, Fosidono- mya, etc., could exist, but later the Cassian fauna enjoyed a varied and rapid development, and lived on good terms with the Reef-fauna of the Cipit Limestones.

o. The fossiliferous marls and Cipit Limestones of Cassian age in Enneberg are succeeded by a calcareous and dolomitic rock, which is of the same age as the upper horizons of the calcareous and dolomitic marine deposits of mid-Triassic age in the south and south-west. Taking one or two parallel lines of section north and south through the inner Cassian belt of deposit, we find that Schlern dolomite succeeds, in the west or Groden area, an extremely irregular submarine relief of volcanic, sedimentary, and reef-rocks of "Wengen and Cassian age ; in the Enneberg area it succeeds reef -rocks and the famous fossiliferous Cassian marls of Stuores meadow; in the Ampezzo and easterly regions it succeeds reef-rocks and fossiliferous marls, belonging to a somewhat later palaeontological zone, Upper Cassian.

6. Contemporaneous faulting and volcanic action were the cause of mid-Triassic heteropism in South Tyrol.

Hence, so far as positive evidence goes, the Coral rocks of South Tyrol in the Wengen and Cassian period are not the majestic mountain massifs of dolomite, but much less obtrusive, lenticular masses of limestone. And one general law may be said to govern the Wengen and Cassian period in Groden, Enneberg, and Ampezzo, a wandering north-eastwards of the Wengen and Cassian fauna (including the special reef-fauna of the Cipit Limestones) consequent on the cessation of volcanic activity along the immediate southern boundaries of the Cassian-Enneberg sea, and the increasing sub- sidence of these areas. During the subsiding movement, sea algse and large Mollusca pressed northward. The shallow-water Cassian- Enneberg fauna, no longer enjoying the same favourable conditions as before, retreated into moi-e and more limited localities and gradually gave place to its lineal descendants, the shallow-water fauna of Raibl times. This transitional period paved the way for the complete recovery of normal conditions in Fassa, Groden, and Enneberg. As Mojsisovics has said. South Tyrol in Eaibl times " participated once more in the general movements of Alpine areas."

{To be concluded in our next Number.)

Geol. Mag. li

Dec. IV. Vol. I. PI. I.

Prolecanites compressits, J. Sby. sp.

Figs. 1-5. Carboniferous Limestone, near Cork, Ireland. Fig. 6. Carboniferous Limestone, Scarlet J Isle of Man.

Foord and Crick Qyi Prokcariites compressus. 11

II. On the Identity of Ellipsolites compressus, J. Sowerby, WITH Ammonites Renslowi, J. Sowerby.

By Arthur H. Foord, F.G.S., of the Eoyal Dublin Society, Dublin; and

G. C. Crick, Assoc. E.S.M., F.G.S., Assistant in the Geological Department, British Museum (Nat. Hist.).

(PLATE I.) (i.) Introduction.

mLIPSOLITES COMPBESSUS, J. Sowerby (Min. Con. vol. i. p. 84, pi. xxxviii. 1813), has been hitherto usually regarded as a Nautiloid,* and referred either to Nautilus or to Discites.

During an examination of the collection of Mr. Joseph Wright, of Belfast, by one of the present writers, a fossil from the same horizon, and almost the same locality as the type-specimens of Elli-psolites compressus of J. Sowerby, was observed, so much re- sembling Sowerby's species (but exhibiting also the character of the suture-line) that a comparison with, and a re-examination of, Sowerby's types was suggested.

Mr. Wright has very kindly lent us this fossil, so that we have been enabled to compare it closely with Sowerby's figured specimens, both of which are in the British Museum (Natural History), and we would take this opportunity of returning to Mr. Wright our sincere thanks for the loan of his specimen, which has served to throw much light upon the character of Sowerby's species.

When describing his species, Sowerby was evidently unacquainted with the suture-line, for, in speaking of the larger of the two speci- mens which he figured, he says "the crystallization seems to have helped to obliterate the chambers, if there were any," and, in referring to the smaller of the two specimens, he says nothing whatever about the septa. After very careful examination we have not been able to detect any trace of septa in the larger specimen, but in the smaller example the suture-line is somewhat indistinctly visible at about the commencement of the last whorl.

(ii.) Description and determination of a specimen in the collection of Mr. Joseph Wright, Belfast.

Mr. Wright's specimen is considerably larger than the larger of the two specimens figured by Sowerby, which, by the way, is a little

' Nautilus compressus, J. Fleming, Brit. Anim., 1828, p. 231 ; id. De la Beche, Geological Manual, 1831, p. 448; id. Goldfuss, in v. Dechen's Handb. d. Geognosie, 1832, p. 536; id. T. Weaver, Trans. Geol. Soc. [2], vol. v. 1837, p. 22; id. L. Agassiz, in E. Desor's Translation of Sowerby's Min. Con. 1842, p. 27 ; id. E. Griffith, Notice respecting the Fossils of the Mountain Limestone of Ireland, as compared with those of Great Britain, and also with the Devonian System, 1842, p. 21 ; id. A. D'Orbigny, Prod, de Paleont., vol. i. 1850, p. 110 ; id. C. G. Giebel, Fauna der Worwelt, vol. iii. 1852, p. 178 ; Nautilus [Discites) compressus, J. Morris, Cat. Brit. Foss., 2nd ed. 1854, p. 308; Nautilus compressus, L.-G. de Koninck, Faune du Calcaire Carbonifere de la Belgique (Annales du Mus. Eoy. d'Hist. nat. de Belgique, vol. ii.), pt. i. 1878, p. 122; Discites compressus, E. Etheridge, Fossils of the British Islands, vol. i. Palaeozoic, 1888, p. 310 ; id. A. H. Foord, Cat. Foss. Ceph. Brit. Mus. (Nat. Hist.), vol. ii. 1891, pp. 86 and 91; id. A. H. Foord and G. C. Crick, Geol. Mag. Dec. III. Vol. X. 1893, p. 253.

12 Foord and Crick On Prolecanites compressus.

largei' than the figure. It is somewhat elliptical, its diameters being 172 mm. and 142 mm. respectively. It was obtained from the Carboniferous Limestone of Little Island, Queenstown Harbour, opposite Blackrock, the locality which yielded Sowerby's types.

The sides of the whorls, especially in the septate portion of the shell, are flattened, feebly convex, their greatest convexity being at about the middle of the lateral area ; the sides of the body-chamber are slightly inflated. In the outer whorl the portion of the lateral area adjoining the periphery becomes somewhat concave. The periphery is flattened, and bounded on either side by a subangular edge ; at the commencement of the outer whorl the periphery is rather convex in the centre and somewhat concave between the centre and the subangular border. As the shell increases in size the peripheral area becomes more flattened, and its edges more prominent (see Fig. 4), so that the concavity of the portion of the lateral area adjoining the periphery becomes more pro- nounced. Eather more than three and a half whorls can be counted, but the central portion of the fossil i.e. up to the point where the diameters of the shell were 11 mm. and 9 mm. respectively is wanting. The inner area of the whorl is well defined, and slopes towards the umbilicus; this slope has probably been increased by the distortion which the specimen has suffered owing to the cleavage of the rocks in which it was imbedded. The slope is apparent, though less distinctly marked on the body-chamber, and where the shell is absent this inner area is scarcely defined on the cast.

The latter half of the outer whorl is occupied by the body-chamber ; it bears only fragments of the shell. One side of the septate portion of the specimen is covered by the test. This exhibits an almost perfectly smooth surface; there are no traces of longitudinal lines on any of the inner whorls. On the last part of the septate portion, that is, on the first half of the outer whorl, there are, however, very faint indications of fine transverse curved lines sweeping forward near the periphery. A constriction near the commencement of the last whorl follows the course of these transverse lines, and doubtless indicates the form of a previous aperture. The form of the con- striction cannot be clearly made out on the periphery. The other side of the last half whorl of the septate portion is denuded of the test, so that the septa are shown very distinctly.

Some fragments of the test remaining on the body-chamber are very well preserved. They show that on the lateral area of the body-chamber the test was nearly smooth, marked only with fine, subregular, faintly-incised lines about one millimetre apart (see Fig. 3), which extend in an almost radial direction over the middle portion of the side of the whorl and sweep forward as they approach the periphery, meeting the margin of the latter at an angle of about 50°, and forming on the subangular margin prominent imbricating lines. These fine lines cross the inner area of the portion of the whorl forming the body-chamber in a rather shallow curve, concave forwards.

Foord and Crick On Prolecanites compressus. 13

Owing to a fracture, a portion of the cast of the body-chamber can be detached from the rest of the specimen. Its anti-peripheral side display's a concave impressed zone, bounded on either side by a