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PLATE I.

ARCHAOPTERYX MACRURUS (Owen).

In the National Collection, British Museum.

8S. J. Mackie del.

THE GE OLOGIST:

~ i MU i OL /)

AS . 7 f\

-

A POPULAR ILLUSTRATED

MONTHLY MAGAZINE

OF

GEOLOGY.

,) —

EDITED BY S. J. MACKIE, F.G:S., F.S.A.

LONDON:

LOVELL REEVE & CO., 5, HENRIETi A STREET, COVENT GARDEN. PARIS: J. ROTHSCHILD. BERLIN: ASHER & CO.

1863.

42. 82054 Qua oq

PRINTED BY JOHN EDWARD TAYLOR, LITTLE QUEEN STREET,

LINCOLN’S INN FIELDS.

PREFACE.

Acatn the pleasant task recurs of thanking my friends for their encouragement and assistance; my only regret being, that the num- ber of contributors to thank is less than heretofore. Those who have lightened by their contributions the labour which otherwise would have devolved on myself, have, during the past year, done me real service.

The papers and letters by my friends Mr. Du Noyer, the Rev. Hugh Mitchell, the Rev. Gilbert M. Smith, Mr. Meyer, of Guildford, Mr. Blake, Mr. James Powrie, Mr. Davies, the Rev. W. S. Symonds, Professor Rupert Jones, Mr. Simons, Professor W. King, Mr. Lech- mere Guppy, Mr. T. Grindley, Dr. Leslie, Mr. J. D. Sainter, Mr. James Plant, of Leicester, Mr. S. R. Pattison, Professor Ansted, Rey. O. Fisher, Mr. E. R. Lankester, Mr. Binney, of Manchester, Count Marschall, Mr. 8. P. Woodward, Mr. H. C. Sorby, Dr. Black- more, Mrs. Strickland, Lieut.-Colonel Nicolls, Mr. Harrison, of Melbourne, and Mr. Drake, are especially worthy of my best ac- knowledgments. The names of some respected former contributors are absent from this list, but the friendship between them and my- self continuing unbroken, welcome communications from them will most likely grace our future volumes. For my own part, the pres- sure of many important labours prevents such entire devotion to

geology as I should like to give; but as far as my power permits,

iv PREFACE.

my best efforts will always be freely devoted to the interest of the readers and subscribers to this Magazine, from whom, so far as they are personally known to me, I continue to receive encourage- ment and support.

I would add here an earnest appeal to country collectors and pro- vincial investigators to send notes of their doings and of the occur- rences in their respective districts: not necessarily for publication, but to put me in possession of the means of securing a most valuable amount of information for the advance of science, which now is never brought before the world, and which passes resultlessly away into oblivion. "When recently at Tynemouth, I observed extensive sink- ings into an unusually interesting mass of boulder-drift, in the con- struction of a new powder magazine for the fort on the éliff within the fine old priory walls. The sections presented were in both north- and-south and east-and-west directions, the drifted materials con- sisting variously of sand, clay, and gravel, all containing flints and boulders of limestone, and other rocks; some, scratched and scored. The gravels commingled with runs of sand and intercalations. of clay, presenting, notwithstanding their intricacy of commingling, evidences of the direction of drifting, not shown in the boulder-clay exposed along the Durham coast. My stay there was extremely limited, yet, although much engaged upon other matters, I found time to make some very rough sketches in my note-book, and to bring away my pockets full of small specimens of as many different boulders as I could. Still, what I did was not sufficient to enable me to give such an account of this remarkable cutting as it deserves ; and as no trace of its existence is, as far as I am aware, shown on the face of the cliff (except, it may be, obscurely on the river side, as far as I could judge from a casual look while walking along the new jetty), there is, perhaps, little chance of such an opportunity for its examination occurring again. If, however, I had been ac-

quainted with any geologist resident in the place, or had any one

PREFACE. Vv

there communicated intelligence to me, I should have had the op- portunity of directing operations, although at a distance, and without visiting the spot,—just as, through Mr. Elliot’s kind and early in- formation, I was enabled to suggest the best manner of examining the Heathery Burn Cave, and of collecting any relics that might be met with in it. Of the mammoth bones at Leicester Mr. Drake kindly gave me immediate information. Of many other similar dis- coveries and occurrences I have also had early notice; but my great desire is to get still more,—indeed, as much as possible,—of such knowledge. Every one who knows me will know thatif the senders wish the information given not to be used, they have only to tell me so, and their desires will be properly respected. The value of re- porting events to some special geologist, is very great, and there can be no better course than to supply such intelligence to the Editor of this Magazine, which is intended especially to record the events of the passing time. I am also pleased to have these pages made use of, as has been done by Dr. Falconer in the concluding number of this volume, as a medium of making known requirements of particu- lar material for valuable labours in progress.

I am also gratified at the free criticism of my own articles, espe- cially when the criticisms are as valuable as those of Mr. Scrope on my earthquake paper. In the speculations I have made, and in those I shall hereafter make, I am not actuated by any desire of in- novation, but wish rather to develop discussions of many points accepted as theories, often only because they are familiar doctrines, and as often on too slight grounds.

In concluding this Preface to my sixth volume, I have only again to express my continued good wishes to my many friends.

S. J. MACKIE.

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LIST OF PLATES.

PLATE To face Page [. Archeopteryx macrurus. . .|- . +. +. - + « .° Frontispiece

II. Didymodon Vauclusianum, Equus macrognathus, and Equus ert we 8 . Equus Chilensis, Equus mactognathus, Bits Devillii, Holoptychius See ery names SOMES eee PE SS . Map of the Greensand Sea. . . ate #4 bin oul ety, oc4 te ee . Coal-Measure Mountains of Arigna Valley df terarr eth’ desporgtide Oe erate On Ariens COOMMCIdS 2. un 2 8 8 st ww we tle OO onan Gn Caen Hoy 8.00. 5 5 pg fete, mye) ey ey eee s wpper Ohaik Clits of Kingsdown . 2. 20.8.) 6 eee oe NBS ES a en, oe a errr | |

. Ammonites varians and Pleurotomaria perspectiva . . . . . . 197 . Ripple-drift, Structure in Mica-schist . . . ...... «+ 201 peevnodne Dubrisioneis, MGs. 6. epee eye ep bw teh en ae nCOnnras SONPICOIB® . ee ee OL EI BEF . Foraminifera from the Chalk of Kent . . . ‘ge it ee . Map of Wealden Area of Kent, Surrey, and nat siricot ert rng ee ono OF A MMIVO Slt, su ee he SRL ne ee ae 2, mou OVI MEl, 5 kb Pe ae) ew Oe Dele a Os el Sema eRMACIVUGEIS-AVIOOMIE ng 8s cute eu km ew “ety wo OL . Stricklandia acuminata . . . ear . . ai> Wey org . Cretaceous Terebratule ; and Wiles aE cial W800.) Gl . Fossil Birds ; Facsimiles from Mylius, Hermann, and Ritter. . . 414 . Fossil Birds; Facsimiles from Kircher and Buttner . . 445 . Fossil Birds ; Facsimiles from Wolfart, Kircher, Retzius, and Ritter 450

LIST OF WOODCUTS.

Page Front View of Brain of Carrion Crow . Beak-like Jaws aes eek of, pe phorhynchus, and Foot of Ar-

cheopteryx . Hee Nodules in Lamoatdiie ‘Siile: ~. £n Nodular Limestones in Carbon-

iferous Slate . . . 23

Results of subsequent Segregation 23

Re-arranged Limestone Band . .« 24 Chelys Blakii eS rae Celts from Chiriqui 45, 46 Elephas Americanus . .. . . 59

Restored Outline of Pteraspis. . 68

Junction of Basal Sandstones and Black Ironstone Shales, N.E. Base of Altagowlan Mountain . 81

Section across the Townland of

Rover . . 83 Section through Altagowlan and

Greaghnaslieve . Diagrammatic Section between

Drumshambo and Drumkerin . 84 Change in Form of Earth . 110 Flint Implement found between

Norwich and Caistor , . 112 Map of Glen Roy District . . £1 Section of Glen Roy, showing Paral-

lel Roads . : . 123 Change in Form of Earth . . 155 View of the Auld Wives’ Lifts. . 163 End View of the “ Lifts” . 164 The Bearings of the “ Lifts” . . 164 Sandstone Block, S.E. of the

“latis? «~ « ; . 164 Boulder near Loch Ken . en Striated Basalt, Loch Doon. . . 166 Island-Boulders, Loch Doon . 166

Page

Erratic Block, Loch-Winnoch. . 168

Stratula passing into Larger Bands 203

Fissures, Isles of Portland . . 210

Shield of Crustacean, Primordial Zone .

Section showing ‘the Portland Fis- sures . « . » 250

Ideal Section, showing Slip of Beds 250

Section of Gully, N.W. Side of Vern Hill, Portland . 251

Shakespeare’s Cliff, Dover . Zeal

Section of the Cliffs from Walmer to Lympne

Ideal Section of Dome- shaped Stra- ta over the Weald, of equal Thickness throughout +

Ideal Section of Strata diminishing in Thickness over the Wealden Area.

Ideal Section of Strata abutting against a Ridge .

Ideal Section of Strata thinning out against a Ridge . .

Forms of Splittings of, Geogra- phical Areas according to their Forms . . . 290

Section of the present Strata across Kent and Sussex, with ideal Out- lines of the Deposit of the Ter- tiary Strata . .

Joints in the ne of the Minti- aghs. . a

Impressions in n the Cambrian Slates 317

Venation of Sphenopteris flavi- CANS «. weenie)

Simple Apparatus for Levelling . 458

Plan of Levelling for Sections . . 459

. 247

- 282

. 289 © ; 289 7 . 290

. 291

THE GEOLOGIST.

JANUARY 1865.

THE AERONAUTS OF THE SOLENHOFEN AGE.

Art least seven geological ages ago, and there were aeronauts in those days. Not Glaishers and Coxwells, clinging to bubbles of gas at six miles high, but reptiles and birds,—the latter at least, and perhaps the former, capable of long and lofty flights. On the red sands of

7)

m

Fig. 1.—Front view of cast of brain of Carrion Crow. ec, cerebral hemispheres ; m, median line ; 00, olfactory lobes ; op, optic lobe ; ss, section of skull; aa, air-cavities.

Connecticut, perhaps some two or three ages before, wingless birds had left their footprints; but nor bone nor feather has the searching eye of man yet looked upon to glean a notion of what those birds were like. Not from all the thick mass of stratified rocks deposited by lake or ocean in the long interval between the period of those im-

VOL. ‘VI. B

2 THE GEOLOGIST.

pressed tracks—persistent through 2000 feet of stone—to the time when a solitary bone was entombed in the sandy mud of the Creta- ceous Sea.*

A little time ago the geological and paleontological worlds were astonished by the announcement of a feathered reptile. We re- corded the reports without comment; the reason was, we could not rightly reconcile the statements to our conscientious content. We endeavoured to procure drawings, but without success ; the specimen was for sale, and no doubt its value would have been prejudiced by its portraits being handed about as “ cartes de visite”’ in the houses of the learned. The accounts that reached us were second-hand and by hearsay. Professor Wagner, on his death-bed, wrote the notice in the ‘ Sitzungberichte’ of Munich, from the description of a M. Witte, who had derived his information from a sight of the specimen in M. Haberlein’s possession. No doubt the mysterious announce- ments of a feathered reptile have enhanced the value of the Pappen- heim specimen to its maximum extent, and have caused it to fetch a price which it never would have fetched had it made its début natu- rally as a bird; but its appearance in the sensation character of a feathered reptile made it a mysterious attraction, and caused it to have, in theatrical phrase, “a great run.”

This singular fossil—a long-tailed bird—is now before us. At page 32 we give a report of the paper read by Professor Owen, before © the Royal Society, on November 20, in which a minute description will be found. Since that time the specimen has been placed in the Gallery of the British Museum, where geologists who feel an interest in this remarkable discovery—and many unscientific persons, too, attracted to it by the notoriety it has attained—have flocked to inspect the blocks of lithographic limestone which contain the singular remains — of the Archeopteryx macrurus.

Professor Owen and Mr. Waterhouse were both satisfied of its true ornithic nature long before the specimen was purchased for the National Collection, and we by no means regret the exceptional expenditure of so large a sum as has been given for it. It is indeed a most remarkable object, and as such, it was most praiseworthy of those officers to recommend its purchase, and of the trustees to ven- ture the risk of blame from parsimonious economists, by acquiring it

* Found, with turtle and pterodactyle bones, amongst the phosphate nodules of the Upper Greensand at Cambridge. It is reported that there has been discovered in the so-

called “ Permian,” but really ‘‘ Rheetic ” rocks of South Carolina, in which Dr. Emmons had discovered, the small insectivorous mammal Dromatherium, the os sacrum of a bird.

MACKIE—THE AERONAUTS OF THE SOLENHOFEN AGE, 3

for that Collection which ought and does take pre-eminence amongst those of all nations, although it is packed so close as not to bea tithe as interesting or as instructive as it could and should be.

and 2, foot of same specimen of Rhamphorhynchus ; 3, foot of Archeeopteryx .— all natural size.

Figs. 1, Beak-like jaws,

Even since the specimen has arrived and been inspected, an article in our contemporary ‘ The Intellectual Observer,’ written with much care and a complete acquaintance with the bibliography of the subject, by Mr. Henry Woodward, of the British Museum, would seem to leave

4. THE GEOLOGIST.

an open doubt that the Archeopteryx might have reptilian affinities, and that Rhamphorhynchus—the most bird-like of the Pterodactyles —might have had feathers, to preen which might have been one of the offices of a horny beak projecting beyond the few isolated teeth set near the fork of the jaws. Neither of these surmises are tenable. The Rhamphorhynchus had long strong teeth—unless we are mis- taken in our interpretation of the excellent example acquired with other remarkable fossils besides the Archzopteryx in the Hiberlein collection—down to the very end of the albatross-like bill or jaws (fig. 1, p- 8); while no traces of feathers have ever been met with associated with any of the numerous débris of those reptiles. As to the Ar- cheopteryx, we are not aware that the inference originally arrived at by Professor Owen and Mr. Waterhouse, that it was a true bird, has been successfully impugned in any way. Those paleontologists who were silently present at the Royal Society’s meeting, or who were “ conspicuous by their absence,’ whose opinions we should have been glad to know, have maintained a significant silence. And the prac- tice of naturalists in this respect seems nowadays like the practice of superior officers in Government establishments,—to find fault when- ever they can, but never to give any praise.

It is most instructive to find in this fossil that more generalized type of structure presented by extinct birds of the Mesozoic age. The birds whose remains have been found in the Triassic, or as modern American geologists suggest, Liassic or Oolitic, sandstones of Connecticut, belong to the Cursorial type. These birds have been placed “ at the lowest step of the scale of ornithic organization.” In the abrogation or non-development of the wings, and in the number and direction of the toes, whose impressions have been afforded to us, we have evidence of a less amount of ornithic specialization in them, and a larger retention of the original vertebrate characters. In the Archeopteryx, the oldest bird of which osseous remains have as yet been found, we have also the retention of the more generalized type, but in another direction. The wings are indeed functional and capa- ble of flight ; the shape of the pectoral ridge on the humerus, and of the furculum, prove this; and the hinder extremities are modified for perching.

But in the twenty caudal vertebre, we see the persistence of the law of generalization. In all embryo birds the caudal vertebre are distinct: as life progresses, anchylosis goes on and they become shortened and united together. The eighteen vertebre in the young

MACKIE—THE AERONAUTS OF THE SOLENHOFEN AGE. 5

os rich are thus reduced to nine in the adult. In the retention of _ the separate vertebre of the tail, the Archzopteryx presents an ex- ample of the persistence of embryonic or more generalized characters,

_ years, that there exists a certain representation of the career of any single animal in the various stages through which the life system of ; * e world has passed.

_ If there be any who yet entertain a doubt of the ornithice character - the specimen, and are misled by the occurrence of Archeopteryx k, in the Solenhofen slate, the very metropolis of Pterodactyles* to

suspect any reptilian affinities for it, we hope that they will compare

the hind foot of the Archzopteryx with that of any bird, and with that of the longtailed Pterodactyle (Ramphorhynchus) from the same Solenhofen beds, in the British Museum. In the birds we see ae foot compact, stout, with an opposable hinder unguiculate digit, _ eapable of prehension or of active support. In the reptile the homo-

DISTRIBUTION OF BrrDs.

Recent. Pliocene. -

Miocene.

Eocene.

b Bee

Cretaceous.

Greensand.

Wealden.

Oolite.

Lias P

Trias ?

Permian.

Carboni- ferous.

S| | {Ez AE |Z

Dimorphodon macronyx . x

D. Banthensis Ae som

Pterodactylus Bucklandii . «|... | s+ | % | oe | vee | vee | vee | vee | coe | coe | woe | oe

P. longirostris ° x a

P. crassirostris . X |...) ven] wee] beep ede. beeen

P. Kochii x -

P. medius x F

P. grandis. > e ¢

P. brevirostris m .

|P. Meyerii . _

pie ane x

P. Fittonii x

P. Sedgwickii

'P. simus . x

P. Cuvierii x

P. compressirostris . x

Ramphorbynchus longicaudus) ..,

6 THE GEOLOGIST.

logous organ is slender, without any opposable digits, and so weak that it could only have afforded a very feeble support (figs. 2 and 8, p- 3). We do see nothing in the Ramphorhynchus approaching t the powerful claws of the Pappenheim long-tailed bird.

The foregoing diagram (p. 5) will afford an idea of the distribution of the various orders of birds in Mesozoic strata. 5

The following table shows the distribution of some of the more— striking types of Pterosauria throughout the upper Mesozoic beds.

DIsTRIBUTION OF PTERODACTYLES.

d

R. Gemmingii

R.

Miinsterii

x

Fossil birds’ feathers have not alone been obtained from the Solen- In the Miocene rocks of Bonn, as well as in Braunkohl, near Aix, examples have been discovered. We are sorry there is a crack in the Archeopteryx stone, and an absent piece just where we would rather not have missed it: that

hofen slate.

»

MACKIE—THE AERONAUTS OF THE SOLENHOFEN AGE. ‘

is, just where we suspect the head might have been. The cranium, it is true, may be still in one or other of the slabs, or it never may have been in either at all. If the bird is the rejected or lost prey of some stronger creature, the head may have been torn off, and with the attached neck, may have been left on the dry ground else- where, or deposited in some other place miles away. But the pre- sence or known existence of the head would have prevented any reptilian mystery ; and the current statement that the head of the Guadaloupe human skeleton in the British Museum is in a museum in South Carolina, causes one to feel a silent hope that by no similar secretive principle muy we be astonished hereafter by the discovery of the head of Archeopteryx in some Continental museum. In the block there is a semicircular portion, apparently of bone, which we have suspected might be a part of the skull; but we certainly should experience something like a sensation of relief, if we were to learn that through the aid of the Museum lapidary, the head was yet existent in the matrix. However, for what we have got we ought to be thankful ; and especially are our praises due to the learned Superintendent of the Natural History Department, for his able, lucid, perspicuous, and convincing interpretation of these extraordinary remains.

Since the above was written, Mr. Henry Woodward has kindly handed us the cast (fig. 1, p. 1) of the interior of the skull of a carrion crow, which has been prepared by Mr. John Evans, F.S.A., who was struck with the resemblance, as he fancied, between the brain of a bird and the little limestone concretion within the bone- mark to which we have referred.

This suggestion was so probable, that we at once instituted a close comparison, and with the assistance of Mr. Carter Blake, we believe we haye decisively made out the actual parts of the brain indicated by that seemingly unimportant protuberance, and for the apt means of the determination of which too much praise cannot be given to Mr. Evans. The story then, as we read it, is that a portion of the skull, and what may be termed the fossil brain, still remain in the slab. We will now attempt to describe this protuberance in the limestone as a fossil brain. The anterior part of the brain is pre- sented vertically to the spectator, or stands out perpendicularly from the face of the stone. At its apex the site of the olfactory lobes are very evident, as is also, running down towards them, the median line.

The inturned edge of the cerebral hemispheres is also easily made out, and some trace of the optic lobe beneath the brain may perhaps

8 THE GEOLOGIST.

posing slab of stone, a portion of the transverse section of the back of the skull, showing the bony intercerebral ridge, is to be met with.

There is near this space a conchoidal fracture, which Mr. Blake thinks might be the impression of the parietal and frontal bones; but although we believe these bones were within the region of this space, we think the conchoidal fracture has been produced by artificial means. The proximity of these cerebral and cranial relics to one of the missing pieces of stone, renders it highly desirable that some pains should be taken to obtain it, as the beak of the bird’s head would have probably projected upwards and inwards into it, as it covered the brain in the slab containing the chief remains. That is to say, the Archzopteryx’s head would have rested on its back on the mud, with possibly one or two of the cervical vertebre attached to it, the beak thus projecting directly upwards, exactly as we usually find those of dead gulls and other birds on our present shores.

This evidence goes far to support the admirable inferences of Pro- fessor Owen, as the fossil brain presents true bird’s characters, and can thus be perfectly distinguished from the very peculiar form of brain in reptiles.

EXPLANATION OF PuaTE I.

c, coste ; sc, scapula; 4, humerus; ~, ulna; 7, radius; cv, carpals ; z, ilium; f, femur ; t, tibia; mt, metatarsus ; p, phalanges ; ca, cauda (tail) ; 4, fossil brain; a, acetabulum ; 1 and 2, carpal hooks,

ON DIDYMODON,* A NEW GENUS OF MINUTE AR- TIODACTYLE MAMMALIA, FROM THE EOCENE OF VAUCLUSE.

By Cuaries Carter Buake, Esa., Lecturer on Zoology at the London Institution.

Since the original foundation of the genus Dichobune by Cuvier,+ and the critical observations made thereon by Owen,{ the national collection has continued to receive new accessions, indicating the ex- istence of a certain range of variation in the molars of that genus.

The specimen (No. 30673) in the British Museum collection, is figured in Plate I1., by Mr. Mackie. It consists of the three molars of the right side of a species of smajl quadruped closely resembling Dichobune. The length of the fractured ramus containing these teeth, of which the inner aspect is exposed to the observer, mea-

* From dfdupos, twofold, and bods, tooth.

+ ‘Ossemens Fossiles,’ vol. v., passim. ¢ Quarterly Journal of the Geological Society, vol. xiii, 1857, p. 254.

.

be detected. Round the back of the counterpart cavity, in the op-

ae

PLATE II.

Fig. 2.

Fig. 3. Fig. 4. 1. DIDYMODON VAUCLUSIANUS: 2. Top View of Molars. (From the specimen, nat. size.) 38. EQUUS MACROGNATHUS (one-fourth linear). 4. EQUUS DEVILLII (one-fourth linear).

S. J. Mackie del.

oT, Pini aye i i : 4 «> i; Kal meets a aS > ; _ “¥ = 4 a -< = ia * 5 : Ps o > 4 7 “ss r ? x “ee : -

‘a

S A ‘U8 AL

ay YORK

~ t ‘ buh rae rw ms

iret

BLAKE—ON DIDYMODON VAUCLUSIANUM. +

sures 27mm.; its greatest vertical depth between the penultimate and last molar being 11mm.

The last molar (m 3) measures 7mm. in length, and 4 in breadth. Its form is quadricuspid; the two outward cusps being least eroded ; from the ectoposterior cusp is developed a slight basal talon, ex- tending towards the entoposterior cusp, which is the smallest of the four, pyramidal, and acuminate; the entoanterior cusp is larger, and is tipped with a small exposed ring of enamel; the ectoanterior cusp is much worn; there is no trace of the distinct hinder lobe of Xipho- don, which lobe in the Dichobune (sp.?) from Hordwell, marked 297148 in the British Museum, exhibits a well-marked bicuspid divi- sion, having the effect of rendering the ultimate molar in that speci- men virtually hexacuspid, to a greater extent than in the Dichobune ovina.

The second molar, 7mm. in length and 4 in breadth, has also four cusps; the ectoposterior one being the most worn, and having a dis- tinct basal posterior talon running from it to the foot of the ento- posterior cusp; the two anterior cusps are much the highest, a sabre- shaped band of enamel running from the base of the ectoanterior cusp nearly to the summit of the entoanterior cusp.

The fractured first molar has the posterior half broken away be- neath the maxillary alveoli; it exhibits the traces of a distinct fang ; its anterior portion shows an eroded surface, affording a slight re- semblance to the bicrescentic contour of the same part in Dichobune.

I have compared this fossil with the specimens, figures, and de- scriptions accessible to me of Dichobune, Xiphodon, Cainotherium, Hyegulus, Amphitragulus, Tapirulus, Aphelotherium, Dichodon, Heterohyus, Acotherulum. Of the latter genus, which closely ap- proached Didymodon, Gervais remarks as follows:—“The Acotherulum saturninum appears to be related to the Dichobunes; but its hinder molars have only 2 tubercles on each ridge, and in this relation it has most analogy with Paleocherus and Cheromorus, for Dichobune has 3 tubercles on the anterior ridge.’’ Gervais figures, on his 24th plate, the 4 antepenultimate superior molars, and 3 inferior molars of the left side. These were obtained from the lignites of Débruge, near Apt. The lower teeth differ from Didymodon, should my inter- pretation of their homologies prove correct, by having a distinct quinquecuspid pattern to the 2nd molar, whilst the 8rd molar exhi- bits (so far as the fractured tooth, half of which is broken aw ay, can yield any decided information) no trace of the well-defined dichoto- mous division of its posterior portion in the new form.

In Heterohyus armatus the last molar is “ tuberculeuse, tres-émous- sée, simulant en avant une fausse colline transverse un peu oblique” (Gervais, pl. xxxv. p. 7), the difference existing between the pe- nultimate and antepenultimate molars of the two forms precluding

* This specimen (No. 29714) consists of the last and half the penultimate molars of a Dichobune ; the former measuring 14 mm. in length and 8 mm. in breadth. In the specimen marked 29856 the cusps on the posterior lobe are worn, the breadth as well as the length of the teeth being much smaller than in 29714,

YOL. VI. C

10 THE GEOLOGIST.

the supposition that any degree of wear could have worn the teeth of Didymodon down to the condition of Heterohyus.

In Dichodon the well-marked bicrescentie form of the molars, and the absence of the tendency to develope 4 pyramidal cusps, with traces of a posterior talon exhibited in Didymodon, render further com- parison unnecessary.

In Aphelotherium Duvernoyi, Gerv., derived from the Paris gypsum, which bears many curious points of resemblance to Didymodon, and which I only know by Gervais’ figures, the view of the lst and 2nd molars from above (pl. 34. loc. cit. No. 186) presents a totally dissi- milar aspect. The two ridges into which the worn molar there de- picted is divided, are more oblique than in Didymodon, while the 3rd molar, which in figs. 13 and 13 is seen concealed in the alveolus, ex- hibits three distinct ridges.

Tapirulus hyracinus, of Gervais, is another closely allied form. In Gervais’ definition of the genus,* he says, “ Lower posterior molars with two very distinct transverse ridges, incompletely united by a weak keel perpendicular to their axis, instead of being oblique; a strong posterior talon; that of the last resembling a third ridge less large than the two others.’’ The posterior talon of the hinder molar in Gervais’ plate (34, 3 and 3*) projects far more in a posterior di- rection than the presumed homologous rudiment in the Didymodon, and this difference is observed in a less degree in the preceding tooth. The ridges in Tapirulus, transverse to the tooth’s axis, are too well marked to render it likely that they may have been produced by the worn enamel-folds of the denuded cusps in an old Didymodon.

Hyegulus collotarsus, of Pomel, which in the other dental charac- ters of its lower jaw agrees with the typical Cainotheria,+ differs from them, according to that writer, in the deeper division of the inner points of the second ridge of its lower molars. The figure of the species which Gervais presumes to be identical with Hyzgulus, and names Oainotherium Courtoisii (pl. 35. f.4, and pl. 34. fig. 6) dis- tinctly shows a third posterior ridge divided apparently into two cusps to the third lower molar tooth. In Cheromorus, from the ac- cessory cusp of the last molar has a tendency to a ternate division, which is seen in the eroded molar of C. simplex, and more promi- nently in C. mammillatus. In Paleocherus, from the accessory cusp, seen laterally, is as high as the two other cusps of the last molar, and even higher than the two median cusps.

Cainotherium, Xiphodon, Dichodon, and Dichobune, each exhibit the same third lobe to the last molar as in Dichodon jf repeating the characters of the two previous lobes of the same tooth. In Dicho- bune ovina, this lobe, probably owing to the less degree of wear in the specimens, assumes more the character of an elevated unequal cusp, which, however, as Prof. Owen has pointed out, “ plainly con-

* Loc. cit. p. 56. .

+ ‘ Geologist,’ vol. v. 1862, p. 32 and p. 124.

+ Owen, Quarter ly Journal of the Geological Society,’ vol. xiii. 1857. pl. ini. fig. 3. The lobe is here marked g.

— =~ , i a . 4 * e “

LG. ety me 2

PENGELLY—ON THE AGE OF THE DARTMOOR GRANITES. 11

sists of a pair of cones; the inner one being rudimentary, the outer one of the same anteroposterior extent as the normal outer cone, but

_ lower and thinner, and oblique in its position.”’ It is this accessory

lobe, which in the ruminant division of Artiodactyla is strongly de- veloped.

In the Amphitraqgulus communis, from the lacustrine marls of Ron- zon, near Puy-en-Velay, the accessory lobe is more outwardly and obliquely developed than in Didymodon, and the same remark applies to the Xiphodon gracile.

I have been slowly led to the conclusion that the specimen in question is not to be identified with any of these genera, from the lower Tertiary deposits. At the risk of burdening the overloaded terminology of the fossil herbivorous Ungulates with a new name, I have been led to give it generic distinction. The specific name Vauclusianum is derived from the locality.

Should it be placed amongst the Artiodactyles, under which order it seems to be categorized, its place will be found near to Dichobune, Acotherulum, and Aphelotherium. At the same time, there is a cer- tain resemblance to Tapirulus, which should preclude us from confi- dently denying that it may have perhaps formed part of the family of small pachyderms, congeners of the great Lophiodontoid Perisso- dactyles.

¢

ON THE AGE OF THE DARTMOOR GRANITES. By W. Peneetty, F.G:S.

Though our science has risen above the stage from which she taught that all granites are parts of the original crust of the earth; though she has advanced so far as to doubt whether, in all cases, the granitic was the first phase of rock-existence which the materials composing it assumed, and to entertain the question whether such rocks may not be the extreme form of metamorphism, which has obliterated all traces of an earlier condition; and though she may prudently decline to point out, in the large circle of her rocky acquaintances, one mass of crystalline unstratified rock which, as such, can be proved to be older than some kuown beds of mechanical origin; it remains to be the rule rather than the exception to meet with persons, frequently well-informed, and not without an interest in geology, who still cling

_ to the notion, or allow it to cling to them, that every mass of granite

is a primitive rock, in the strict chronological import of the term; and represents a period in the earth’s history prior to the possible existence of sedimentary strata, or of organized beings. Indeed the opinion that granite is, in all cases, a primary rock, has so large a place in the public mind, that one might prudently hesitate before

‘ throwing such a question as “ What is the age of the Dartmoor

_ granite?” before any audience having a very large admixture of the

_ popular element.

12 THE GEOLOGIST.

It has long been known that the age of the granitic rocks of Dart- moor can be safely limited on the side of antiquity. That they are less ancient than the culmiferous beds of North and Central Devon has been established on satisfactory evidence produced by various observers.

Sir Henry De la Beche, in his ‘ Report,’ says, “The intrusion of the Dartmoor mass was certainly after the deposit of the carbo- naceous series of North Devon, be the age of that series what it may ; it thrusts the southern portion of this series northwards to Oak- hampton, cuts off the ends of trappean bands and of associated beds of grit and shale near Cristow and Bridford, and sends veins into it in the valley of the Dart, at the junction of the two masses of rock.’ *

Professor Sedgwick and Sir R. I. Murchison, in their paper on “The Physical Structure and Older Stratified Deposits of Devon- shire,” say, “ Granite veins, passing from the central mass into the superimposed stratified rocks, are found on all sides of Dartmoor. We have seen them above Ivybridge, injected amongst the oldest slates of Devonshire; and near Oakhampton we have seen them in lke manner, penetrating the culm-measures; and they are finely ex- posed in the beautiful gorges of the Teign and the Dart, where those rivers descend from the granite to the culmiferous series. These ex- amples, to which we could add many more, are sufficient for our pur- pose. Now these veins, taken in general, are mere prolongations of the central granite, inseparable from it, and contemporaneous with it; they cannot therefore (as the granite is one mass) be contempo- raneous with stratified rocks of different ages. Consequently they are true veins of injection, and the granite was protruded at a time posterior to all the other stratified systems.” In another part of the same paper these authors go on to say, “It appears that the rocks of Devon and Cornwall belong to three periods of formation. The oldest includes the various groups of slate rocks, and at least a part _of the associated traps. The next includes the culm series, the upper division of which contains fossils identical with those in the upper