I . . Ua).on I". Nopcscc-Britislb .Din oscru~~s. 109

,ttiug in of the severe climatic conditions which caused the formation of the head.

Ii review of the various measuren~ents quoted above and a con- , i ~ ~ ~ ~ t i o n of the mnximum heidits of tlre platform in the different

(see Fi5. 4) would seem to indicate some deformation of the ,horeline. O W L I I ~ , however, to the possibility of cri~llulative errors of bbservati01l, to the probability that the inner angle did not always befir the same relation to high-water mark, and to the subsequent cst,cnsire modification by glaciation, I do not a t present wish to lay nlllcll stress on this point.

Having up to the present avoided all consiclerations of a speclllative nnture, I may perhaps be permitted in conclusion to suggest a working ~ , ~ ~ o t h e s i s . It is well known that the late-glacial 100-foot bench is

to certain parts of Scotland, being absent in Enpland, rel land, and the extreme north of Scotland (Caithness) (see Fig. 1). Tllroug'ho~t its area of distribution it maintains, moreover, n fairl-y lllliform level of 100 feet above the sea, and vhere it disappears i t docs so abruptly, not dipping gradually belor sea-level like the 2.j-foot beach. NOW the (0 to 12-foot) preglacial beach of Southern 13ritain has not been traced within the area of the 100-foot beach. Well within this area we find, howe~er , the (100 to 135-foot) pre- (rlaeinl beach of the Western Isles. Now, makinq the admittedly '7

(la11 gerous correlation bet~veen the two preglacial beaches, t 1s e tlp~noxi~nate coincidence of figures suggests that the moven~ent (possibly block-faulting) mliich brought the 100-foot late ~ l a c i a l beach into its present position was also responsible for the elevation of the preglacial beach in the Western Isles of Scot1;ind.

II.-;1\Tur~s ON BI~ITISII DIXOSAURS.~ P..\n.r I V : STEGOS~-~C;ZIU,S PZISCLT,C,

SP. KOY.

By Baron FRANCIS NOPCSI. (TVITH NINE ILLUSTRATIONS I N THE TEXT.)

S I WCE the O)~cosnurus of the Iiin~eridge C1:ty lnay still be regarded as the only well-known European reprosentatire of the Stegosauridce,

i t seemed advisable, af terdiscussing in previous papers the Orn~thopodous I&/psilo21l~odo?2 and the Acnnthopliolidici Polncn?2tltus, to examine n repre- scntntive of this type. I urn therefore greatly indebted t o Dr. A. 8. ~\~ooclmard for permitting rue t o do so a t the Natural History Ilfusenm, nud ttlso for putting a t mv disposal a magnificent hitherto undescribed Stegosaurian discovered hy Mr. Alfred Leeds, F.G.S., in the Oxford Clay of Fletton, near Peterboroltgh.

On account of the small elevation of the neural arch of the dorsal yertebrze I propose to name this new Stegosauriali species Stegosnz6l.zls ~ ' ~ S C Z C S .

The type-specimen of St. priscus in the Katural History JIuseum I)cnl.s the register number R. 3167, and is represented by numerous

Part I, Hypsilophodo~z, with a, page illnstratioll, appeared in the GEOL. MAG., 1905, pp. 203-8 ; Part 11, Polncnntltzu, op. cit., pp. 241-50, with Plate XI1 i ~ l d S text-figures ; Part 111, Streptos~~o~zcll~Zz~s, op. cit., pp. 289-93, Plate XV (all in Decade V, Vol. 11, 1905).

bones ; a secoud iud i~ idua l , of which the distal end of the pubis.and some dermal plates have been described by von Huene as Stegosnurua sp.,' is in the Sedgmick Museum a t Cambridge.

The type-specimen of S t . priscus is rcprcsented by thc following material: 2 nnterior cervical vertebrs including the axis, 9 dorsal re r tebrs or fragments of such, 15 caudal rertebrse, 1 cervical rib, fragments of cherron bones, 3 left and 1 right dorsal ribs, the right humerus and ulna, the left feniur and parts of the corresponding tibia and fibula, carpal bone, astragalus, and calcaneum, fragments of both ilia, parts of both pubic and ischiac bones, parts of t l ~ c dermal armour.

FIG. 1. a. Axis of St. P T ~ S C U S seen from the right (most of the neurnl spine wanting). b. Anterior cervical rib of same. c. Dorsal vertebrn of the same. d. Middle caudal vertebra of the same.

Pertebr@.-The axis of the Fletton Dinosaur is of special interest, for hitherto no axis of a Stegosaurian has ever been described or figured. It is 12 cm. long; a t the posterior end i ts body is 4.8 cm. wide and 4.5 cm. high. Unfortunately the neural arch is much mutilated, as shown in Fig. la.

The odontoid projects far forward; the centrum is strongly compressed laterally, but as shown by the irregular split-like section of the neural canal this is to some degree due to post-mortem cleformation. T h i ~ dcformation has also cnusect thc basal lreel of the ccntrum to be more

Centrnlblatt fiir Mineralogie, Geologie, und Palaeontologie, Stuttgart, 1902.

marked in the fossil than it may have been in tho living animal. The anterior and inferior margins of the centrum show strong rugosities. On the posterior margin two hypapophysial lrnobs are present. Thc anterior nrticular surfarc of tllu ccntrum is plane, thc posterior llloderatcly concavc ; both surfaces show a straight superior and equally rounded lateral and inferior border, having thus the shape of a circular disc, of which a segment is missing.

T l ~ c nrtici~lnr surfilccs for thc lirst ccrvical rib arc sitrlntcd on thc anterior superior part of the centrum, and on tlie middle of tlic arch immediately above tho ncuro-central suturc. The neural arch is m11c11 mutilated, and only one post-zyg:~popligsis is preserved, which is situntctl comparutirely high above the centrum. I t s articular surface is not clearly defined, and is directed outward and downward.

With the exception of i ts being a few millimetres shorter, the second vertebra, of which only the centrum is preserved, has practically tlre same shape as t h e axis, the chief differences being the stronger develapnlent of thc hypapophysial ltnobs and the evidently more elevated pleurapophysis, for no trace of it can bc found in the part preserved. Compared with the cervicals of the nenr 0. Lewnieri, preserred a t the Havrc Museum, thc description of which will shortly be published else\vhere, there is a grcat differencc in the laterally compressed centra of St. prisczrs aud $so in the rectangular shape of the neural platforln (Hullje), which is sandal-shaped in 0. Lennieri, being strongly contracted in the middle. No great difference between the cerricals of our Stegosaurus and the American Stegosac~rus is apparent.

It does not seem improbable tha t the left triradiate cervical rib, represented in Pig. 16, belonged to this or to the following ~ e r t e b r a , for the distance of the capitulum. and tuberculum mould correspond to tlre proportions we slrould cspcct to find i n thcsc rer tcbrx if thcy were complete.

Besides two processes for thc cnpitnlum and tubcrculum and tlre comparatively short and flattened body of the rib, this b,one shows on the exterior par t a \veil-marked excrescence, which is represented in most Dinosaursollly by a feeble ridge, but is well developed, though with altered direction, on tlic cervical rib figured by Marsh as a rib of Apntosauvus. I n Stegosaurus this excrescence is pointed outward and forward, ~ n d it may perhaps be best compared with the dilatation. of tlie cervical ribs in some Lncertilia. It iuay have serred for the purpose of combining a limited amount of flexibility with strength in this region of the body. A quite similar, though more ridge-likc excrescence is also met with on the thoracic ribs of Ste.qosaurus, and produces therc, together with a similar posterior ridge, t h e obliquc T-shaped cross-section tha t has been specially noticed in Stegosnz~rus, but seems, as far as I am aware, to be present also in other members of the Orthopodous order.' I t s origin may therefore have to be explained otherwise than through tlie meight of the dermal armour.

The dorsal vcrtebrz of St. yl-iscics (Pig. I c ) approximate in gcneral

I would suggest tlint tlio Dinosnuriy.ns represent a distinct super-order, which may be divided into two orders, Saurischia (Seeley) and Orthopoda.

to the type of St. zilzguZatz1s and 0. rcrmatus. Several differences, 4 Ilomerer, may be noted as distinguishing this species quite clearly from either of the others. 4

I u St. z~~~gz~katus the point from which the diapophysis arises is much highor above the bottom of the neural canal than in our specimen; 3 i n 0. nrnzatzis this point is very much lower. Corresponding mitlr this difference the elevation of the prezpgapophysis in our specimen , is also intermediate between that in tho two other animals; while '

0. Lcnnioi shows much the same stage of specialization as 0. nmzatus. 'l'he direction of the diapophyscs is also different i n the different unimnls, for tho7 areclirccted more outward thau upmarrl in 0. rcl.nzrctzc~, more upward than outwnrcl lr. St. zlngzilatzis, nncl equally outward

FIG. 2. Dingram illustrating the difference of strain on the diapophysis as coi~elated with the elevation of latter. a. Stegosaurian type. b. Ornosaurian type. p = pnn~pophgsis ; d = dinpophysis ; x = weight of dernlal a inour acting on the rib by ?IZ ; y =.amount of vertical pressnre ; a (a') = pressure on parapophgsis ; B (8') = strain on dinpophysis.

and upm:~rcl in St. yri.vcus, the angle tha t they form with the neural spine being in the latter just about 45 degrees. Comparing these d:ita with Scelidostctc~z~s, me remark tha t the elevation of the diapophyses steadily increases as these animals specialize. Since the bones of these animals are not pneumatic, and since a similar elevation is not present in the marnmalia, tho~lgh in these the development of lungs is mncli nlorc importnnt than i n reptiles, I (lo not bclierc this elevation had anything to do with the development of the lungs as generally accepted, but I thinlc it is rather duo to t l ~ e increasing *

Stegosaurzn ~J)-~scz~s, sp. I ~ O C 113

: . . To illustrate this the diagrams Fig. 2a and 2b were drawn according to the evidence affordcd by 0. armatzcs and St . u?zgulattcs. By breaking

: up in these figurcs the -vertical pressure of the dermal armour on the rib y into i t s co~nponents u ( r ~ ' ) and 13 (PI), it becomes clear tha t in St. un.qzclntus (Pig. 2rs) the strain ( P ) on the diapophysis (d) is by

s (Pig. 26, P') while the

ssure a (u') on the parapophysis (p) is augmented, for d = $ and

(1 animal, the increase lting from the lateral this animal not be of

. . Two other quite marked features of the dorsal vertebreof S t . p i s cus , . in which this anirnal'makes a close approach to S t . ungzclatus, are the : ' lateral compression of the neural canal and the absence of cavities on

i: the sides of the centrum. The shape of the transre~*se and longitudinal : . sections of the plano-concave centra seem, however, otherwise to be t h e . : stime in both Omosaurs and Stegosaurs.

t . prisczts, but the proximal

T h e middle caudal vertebrse (Fig. I d ) of St. priscus have the neural spine more elevated than in 0. wmatur, but not cleft a t the top as in St. ungzcZatas. 'l'he section of the rod-like neurapophysis is triangular a t the base, but oval and somewhat laterally compressed a t the summit. The post-zygapophyses are not much elevated above the neural canal, they are directed both straight downward and outward. The pre- zygnpophyses are correspondingly directed upward and ontwnrd. The '

FIG. 3. a. First (?) caudal of St. prkcus. b. Proximal caudal of the same. c. Anterior view of distal caudal. d. Lateral view of the same.

moderately short centra of these vertebrse are concave a t both ends, more so posteriorly than i n front ; the sides are flat, the bottom keeled, the articular sal-faccs for the chcvron bones largo, equally dcvelopcd a t both ends, and nearly touching each other on the basal ridgc. Tiley , are not easily distinguishable from the rugosities tha t occur round the

I;: R. C. Reed-New &.tcstucea, Isle of Wight. ,116 . .

' margin of the articular ends of the centra. The costoids in the middle of the tail are rod-like elements, decreasing rapid17 in size backwards. There is a great resemblance to the middle caudal vertebrs in St. ungulatus.

The distal cauclals in SL. priscz1s, as shown in Pigs. 3c, G?, are still more elongate thnn the middle ones. The centrum is laterally compressed, as F I ~ . 3c shoms, and exhibits a pentagonal section, with the point of the pentagon turned downn~ards. The articular surface for the chevrou bone on these vertebrs is only developed a t the posterior end. The concavity of the articular surface is also more marked a t this end than at the other. The neural arch in these vertebm, as in all the anterior ones, covers nenrly the whole of the neural canal ; the elongate rod-like prezygapophyses are comparatively feeble, their articular facets are directed as in the middle dorsnl<. The narrow neural spine (Fig. 3d) rises in a rcnlnrkable manner straight upwards; i t is blade-like, tapering towards its summit, and, like the rest of this vertebra, i t is characterized by the complete want of rugosities, thus indicating clearly that on this bone no great mass of firmly adhering tissue mas present during life. This latter observation will prove to bc of the utmost importance whcn we discuss the dermal armour of St. priscus.

The distal caudal in St.priscus differs from that of St. zing~ilcttc~ and Dirncodon by the feeble development of the neural spine, and still more by the development of elongate post-zygapophpses, for these are quite short and nearly sessile on the blade of the neural spine in St. ungzclatus, Diracodo7t, and many other Dinosaurs, though not in Polacanthus. Tlle development of the neural spine and the post- zygapophyses in St. priseus are features so strange for a posterior ca~ldal that if tho shnpe of the centra did not prove beyond all doubt the contrary, one might hesitate to refer this vertebra to an Omosaurzcs. Tlie biconcave nature of all the caudals of our Slegosazirus, and the neural spines overlapping each other, do not imply great flexibility of this organ.

(To be co~uluded irc OUT next Nzcmber.)

I~I.--SED(~\VICK ~ U S Y U Y KO'~'YS. NEW CRUSTACI-:A PRO31 THE LOWER GREENSAND O F THE ISLE O F W ~ G H T .

By F. R. COWPER REED, M.A., F.G.S. (PLATE VII.)

TGST tho large series of specimens of ~lfcyeria recently I AMoh obtained by the Sedgwick Museum, Cambridge, from the Lower

Greensand of Atherfield, lsle of Wight, two nem and strange forms, obviously referable to another genus, were detected by me i n looking over the material. Their interest consists not only in belonging to new species but in repsesenting the genus Thenops, of which the best known and only British species, so far described, is Th. scyZlarifomzis, Bell, from the London Clay. There is one imperfect specimen in the British Museum from the Speeton Clay attributed (with a query) to I'honops, but no otllcr British rcprcscntativo from tho Cretnceous appears to have been found.

G1ICOLOGICA.L MAGA % I N E . NEW SERIES. DECADE V. VOL. Vill.

NO. IV. -APRIL, 1911. I -

ORIGINAL ARTICLES- - *-- -

1.--Noar~s ON 3it11.1s11 DIXOSAUILP. PART I V : STEGOSAURUS PRISCCS,

SP. XOV.

By Baron FRANCIS NOPCSA. (WITH NINE ILLUSTRATIONS IN THE TEXT.)

(Colzcluded from the March Number, p. 115.)

Limb-bo?zes.-Since the humerus is known in ByZaosaurus (?), Onzosaurus, and Stegosaz6rus, it is quite easy to ccmpare the humerus of our new species with that of the other genera mentioned. Whether the shaft is hollow as in Omosaul-us or solid as in Ste,qosnurus, cannot *

be ascertained without breaking the specimen ; the outline of the new humerus is, horneyer, that of Onzosaz~rz~s, not that of Stegosau~w.

FIG. 4,. Humerus of St. priscus. a. Posterior view of proximal end.. b. Anterior view of distal end.

The proximal cond~le was situated, as far as can be made out, much as in 0, armatus, and the radial crest shows also the same curve as in this species ; the anconeal ridge, however, is more strongly dereloped, and ends distally in a broad rugose area somewhat above the middle of the bone (Pig. 4a). The anconeal depression and the trochlear . groove (visible in Fig. 4b) 'are less marked in St. y~iscus than in 0. armatus. The ridge for the supinator is broken off in the new specimen, but if preserved it would give to the distal part of the bone a rather 'dilated aspect, and thus produce a certain resemblance to St. u?lgzclnttls.

DECADE V.-T70L. VII1.-NO. IV. 10

Though the humerus me are considering has been son~ewhat flattened by crushing, the inward bend of thc radial crest docs not seem to hare becn as strong as in. the humerus referred by Hulke to IFylaosaurus, with which i t might otherwise be well compared. The total length of the humerus is 50 cm.

T h e ulna of 0. arrnntu.~ is too much nlutilated to be compared with the same bone in S t , prisctu. If, however, me conlpare the ulna of Stegosaurus, we find tha t it is less dilated a t the proximal end and tha t its shaft is much more slender (Fig. 5). The length of the ulna from the hume~xl articular surfuce to t l ~ c dist:il end is 4 0 cm.

A large irregular flattened bone of somewhat parallclopiped shape, the structure of which mould indicate that i t was almost completely covered by a t l ~ i n layer of cartilage, may be regarded as a proxin~al carpal, though from lack of comparative material i ts position cnnnot ye t be deternlined with precision.

FIG. 5. Ulna, of St. pr i scd .

According to Marsh separate carpals characterize the genus Diracodon, and this would tend to indicate a close affinity between our Stegosaurus and this genus, but I am quite open to the suggestion tha t such a fusion of carpals i n some Dinosaurs may be due only to old ago, and hence may not have either generic or even specific value.

The femur of the new Stegosaurus (Fig. 6 0 ) is a long, straight, and rather slender bone, somewhat compressed from back to front a t each

Stegosazcrus priucus, sp. itov. 147

end, and showing a well-developed articular surface suggestive of that in the femur of a chicken i n which the epiphyses are not yet fused with the bone or h a w been artificially removed by roasting and boiling afterwards. The articular surfaces on the femur of St. priscua are not flat but rugose, and show irregular grooves and furrows resembling those of the bone-surface to which the epiphysis is attached in birds and mammals. The manner in which these s ~ ~ r f a c c s pass into the rest of the bone is liltewise the same as in thc strongly macerated chicken just mentioned. The lack of a pit for the attuch- ment of the ligan~entunl tcres is another notewortlry feature of St. p).iscus and 1111 S tegosa~~r idz , and the whole character of t l ~ e articular surface is entirely different from that of the Ornithopodous femur where a pit for the ligamentum teres is indicated. To sfio\r the differcnces here referred to, a strongly macerated femur of Gallus

FI~. 6. Femora of various animals. a. Strongly macerated femur of Gallus. b. Non-macerated femur of the same. c. Femur of St. priscus. d. Femur of Hypsilq'hoda Foxii.

(Fig. 6a) and another which has not been macerated (Fig. 6b), besides a well-ossified femur of Hypsilophodon (Fig. 6 4 , showing t h e pit for the ligamentum teres, and the femur of S t , prisczcs, h a r e been drawn together of equal size i n Fig. 6, and i t is thus easy to see between which bones there is the greater resemblance. I do not wish to imply by pointing to these similitudes thdt Slegosazcrus had separate epiphysial bones, but I wish to emphasize the fact that i n this genus the a m o ~ ~ n t of cartilage on both cnds of the femur mas decidedly iuucli greater than in the Ornithopodidse, and that the shape of the proxinial and distal end of the bone must have beeu originally somevhnt ditfercnt from the present shape. The lack of a trochlea on the distal crid of tlie fclnl~r of St~,qosnurus can give us a cluc to the amount of cartilage missing, for Ste,qosaurus, bcing a terrestrial animal, cannot have walked, and especially sat down without bending its

' 148 Barojz I". Nopcsa-Br.itish Uiuosnu~.s-

knees sometimes for more than 90 degrees, while as shaped in the fossil the tibia would become dislocated if forced to make an angle of wore than 45 degrees with the femur. This tends to show that the

thick, and this is certainly not too much when we consider that the 1 cartilage on the distal end of thc fcmnr n i ~ ~ s t have been a t least 4 cm. ,

distal femoral cartilage of the macertlted Gollus figured above had a thiclrness of 4 5 mm., while the femur itself measured 94 mm. in , length. It becomes evident that just as we could never try to bring . the macerated femur of Gallzcs into correct juxtaposition to the '

acetabulum without allowing for a great amount of cartiluge, so we cannot base any conclusion a s to the position or direction of the femur in Ste,qosnurlcs exclusively on the shape of its articular surface ; and this must be emphasized all the more since such an attempt has recently been made by Tornier in regard to the similarly-shaped femur of Diplodocus. The reason why the discussion of the femoral cartilage caps of Omosazc~us needs to be so detailed is, tha t Tornier has recently expressed the belief that the similarly-shaped femur of Diplodocrcs was only covered with a few millimetres of cartilage.

Even by those who hold the contrary view the amount of cartilage in Biplodoczis is thought to be correlated with the aquatic habits of this monster, but this theory cannot apply to the heavily armoured Stegosaurs. I quite believe tha t the feeble ossification of the sternal apparatus and the low degree of ossification of the distal carpals and tarsals in most Dinosaurs are much more likely to explain the great cartilage caps on the femora of the Stegosaurids and similar animals than the hypothetical aquatic habits. These features and the coarse structure of the bones indicate a low degree of ossification in the whole body, and the great masses of cartilage were probably needed to ensure the continuous increase of sire throughout life. Perhaps this was one of the causes for the rapid extinction of the Sauropoda.

Besides the development of the so-called articular surfaces, the feeble development of the fourth trochanter is an interesting feature in the femur of our new Stegosaurzcs. According to Marsh's description the femur of the American Stegosazcrus shows no madred fourth trochanter, while St . durobriwnsis bears this process. The femur of the type- specimen of 0. armatus is too badly crnshed to show this feature ; on 0. vetustus, according to F. yon Huene, there is no such process. 0. Lennieri shows a rounded but marked swelling with a rugose surface that can well be called a distinct fourth trochanter, and S t . priscus bears on the interior posterior surface, rather high up on the shaft of the bone, an obtuse swelling, which dies out very rapidly both upwards and downwards, and must be considered as the last trace of this trochanter. It may be concluded thut the variable developlnent of the fourth trochanter affords a good character for distinguishing the different species of Omosaurs and Stegosaurs.

The tibia and fibula (Fig. 7 ) are represented by more than half of each bone in St . princus. Like in the Ceratopsidze mid St. ungulatus, t l ~ c strong tibia is distally enlarged and flatterled on the antcro- exterior borcler for the recoption of the fibula. Bo t l~ bones are so closely applied agninst each other and to the fused calcaneum and astrilgalus that this part of the foot formed one inflexible piece.

Stelloshirrzts priscus, sp. not-. 149

Although the tibia is imperfect at i ts proximal end its length can be estimated a t 57-60 cm.

Since, ao already mentioned, the femur of St . prisczrs measures [ 90 em. in length, the ratio of tllesc two bones in this species is 2 : 3. ' while according to &1ilitrsh1s figures i t is something lilte 7 : 4 in i st. ungulatus.

FIG: 7. Anterior view of tibia and fibula of St. priscus.

The ratio between humerus and femur i s : 1 : 2.3 in St. ungzrlatus; 5 : 9 i n St. priscus; 4 : 5 in 0 . armatus. Thus, in the length of the limb-bones St. przsczcs is intermediate between the two other forms.

Pelue's.-With the help of Nr . D. N. S. Watson, of Manchester, three most unpromising pieces of bone have been made out to represent pieces of the ilia. The left post-acetabular process and portions of the margins of both ilia just near the acetabulum are present. Though not very characteristic and rather crushed, the post-acet:ibulnr process agrees in its slender shape rather with 0. Lerznicri and nrntatus than with Stegosaurus, b u t the absence of the rest of the ilium is t o be rcgrettcd all the more, since this bone is the 111ost characteristic for separating the genera Omosaurzcs and Stegosaurus.

Sfeyosrrllr*tta priscz~a, .y. lot.. 151

a longitudinal cleft occurs between these two bones. Compared with the ischium of 0. armntus (Pig. 8a) i t map be seen that tho distal half, though i t 116s on its upper margin the notch cl~aracteristic of Stegosnuvzcs, is much more slender in St . priscus, but the flat, desk- like s l~apc is the san~e in both animals. I f we compare this type of ischium with the same bone in St. ungulatus or 0. Lennieri me find a fundamental difference, for in these two genera the ischium is not flat but twisted, and the superior margin of the ischium curves in

'such a manner as to meet in the median line a t the proximal part of the ritther loug isclliadic symphysis, so that a great part of the iscl~iunl is thus modificcl into a horizontal plate that overlies the pubis. I am a t a loss how t o esplain this difference in two forms so closely allied, for i t seems difficult to explain it simply through post- mortem pressure. The longitudinal cleft between the pubis and the ischium, which is present i n both species of Omosaurus and our Stegosnurian, is u character found in all primitive Ornithopoda; the closing of this cleft observable i n St. ungulatus must therefore be regarded 11s a mark of specialization.

To facilitate a comparison of the ischia of 0. armatus and St.priscus i t has been thought advisnble t o figure these bones of both species near each other, and this seems al l the more necessary because the pelvis of 0. armalus has never yet been figured in the proper position.

Dermnt drmozcr -Associated with the bones just described several barlly crushed pieces of dermal arn~our were discovered. Both spines and plntes arc present.

The plntes are somewhat asymmetrical. Towards their base they are rounded and equally rugose on the exterior and interior margin, thus proving that they rose nearly vertically out of the skin ; since, however, they are all more or less in a fragmentary condition, i t seems enough to pnblisl~ only a diagram of the transverse section (Fig. 9a) to show how tllis kind of plate would be inserted in the tissue of thc body.

Tl~ough as badly prescrvcci as the plates, the two spines found among the material show such peculiar features as to justify a more detailed description. The fragments are nearly similar, and include in hoth cases the base of a spine and its attachment-surface. The height of the specimen figured is 29.5 cm., its breadth 10 cm., its thickness a t the snmmit 2 . 5 cm.

Of the upper part probahly three-fourths or more is missing, but the base is entire and scarcely deformed by crushing. The piece shows an anterior and a posterior ridge, a more concave outer and n flatter inner surface, the latter being divided into n superior and an inferior half. On the outer side (Fig. 9b) a t the base only a narrow rugose margin is observable: on the inner side, however, the rugose area reaches much higher (Pig. 9c ) and occupies nearly half of the fragment, making an obtuse angle with the upper half of the spine. The great extent of the rugosity on the inner surfuce and the f l t~ tne~s of the surface over which the rugosities extend prove that while the exterior part of the bone was only slightly embedded in soft tissue, the interior side continued to adhere to the skin up to a much higher point; hence we may conclude that this spine rose, as indicated in

J

e

Fig. 9d, very obliquelv from the body, or else th:it the curve to which it was attached mustdhuve had a t least a diameter of 80 cru., if not much more.

As the lack of rugosities and the small size of the later ccudals show that the end of the tail of St . yriscus was not coveretl by powerful muscl(>s and can scarcely have attained a diaketer of 40 crn.", i t is evident that these two particular spines of St . yriscus cannot have been situated on the tip of the tail, but must hare been on some other part of the body. Leaving the shape of the spines entirely out of consideration, and judging only from the evidence afforded by the other armoured European Dinosaurs, notably Scelidbsazcrus and also Hyl~osaurus and Pokccanthzcs, one would never be induced to place the dermal spines on the tail of our Stegosaurinn, but on the scapular region. This determination is apparently supported by the shape of the actual surfaces of attachment of the bones in question.

FIG. 9. a. Transverse section of dorsal dermal plate of St. prisczbs, with indication of hypothetical attachment to body-tissue. b. Exterior view of spine of the same animal. c . Interior view of the same piece. d. Marginal view of the same piece, with indication of hypothetical body-tissue.

Conclusion.-As already poin tecl 011 t in the course of this paper, St . prisczcs agrees in the stage of evolution of i ts dorsal v e r t e b r ~

- somewhat with St. zcngulatzc.~, while in its limbs i t holds an intermediate position between 0. nr~?zntz~s ancl S t . ~zc?zyzclntzis. I n its pelvis it corresponds with the genus Stegosaurzcs, though representing a new species.

Considering the developnlent of the preacetabular part of the iliunl as a generic character, we i1la~ arrilnge the members of the genera Stegosazcrz~s and Omosnzt?.us in the following manner :-

Genus O a r o s ~ n ~ n s (Owen). Ilium not yery elongate anteriorly, widening backwards rapidly towards the acetabulum and the first sacral vertebra, its anterior extremity rouncled. Neural arch of dorsal v e r t e b r ~ slightly elevated. Five sacral ribs present. Sacrum much depressed from top to bottom.

0. at.)l?atus (Omcn). Dorsal vertebrae with lateral pits; sacral vertebrre not n~ncli :~l)brcviated. ltatio betweeu humerus and femur 4 : 5 . Articular ends of feniur not nl~lch expanded.

0. Le?znieri (Nopcsa). Dorsi~l vcl-tebrae nritl~or~t lateral pits ; sacrnls strongly abbreviated. Fourth trocllan ter feeble but well rnarlred. Articular ends of femur not mncll expanded.

0. celustu.~ (Huene). Articular ends of femur ~l~oderiltely expanded, rnithout fourth trochanter.

Genus S . r~~osaunus (;"\larsh). I l i~tnl very elongate anteriorly, its breadth invreasing onlv gradually backwards. Four sacral ribs present. No very p e a i dorso-rentral compression of the sacrum. ~ r t i c u l a r ends of femur not expanded.

St. durobricensis (Hulke). Femur wibh strong fourth trochanter. St. priscus (Nopcsa). Neural arches of dorsal r e r t e b r ~ moderately

elevatecl. Femur with rudiment of fourth trochanteri Ratio of humerus to femur 5 : 9.

St. tnzyulatus (Marsh). Neural arches of dorsal vertebrz very much elevated ; sacruls not mucli zibbreviated. Femur witllout fourth trochanter. 1tatio of hunlerus t o femur 1 : 2.3.

By H . M. BRYDONE, F.G.S. (Co?tti?zz~ed front Decade V , Vol. VII, p. 463, 1910.)

(PLATES I X AND ' X.) P .~~OLUNULIKES SCA~DI<NS, sp. ]lor. P1. 1X, Figs. 1-4.

Zonriuna free, unilaminttte, the baclc diiided by somewhat wavy, shallo\r-, slightly diverging fol-rows into long narrow strips nll~icll .correspond wit11 the lines .of zomcia; these strips arc occasionallv . C ~ O S S ~ ~ by rery shallow depressior~s 0;. furrows c;rresponding to t h i boundaries of indivi(lua1 zoacia.

Z o ~ c i n clispoeed in gently diverging and out~ard-curving lines, which are i n some places confluent and in others separated by ~ibracular ia; they are short and broad, with bulging sitles, but very variable in size anci ontline, average length .55--6 inm., breadth (~~laxinnum) -6 111111. ; the baclc wall w r y soon leares the back of the zoariuru and rises gently but steadilv u p to the let-el of thc front wall a t the 11ead of the zomcium, and the succeeding zoceciurn grows out fro111 beneath i t ; in the shallow part of the b:tck lvall mar sometimes be obschrsed a pair of large foramina ; the aperture dis terminal and large, oecnl,jing the upper two-thirds of the area, irregular in size and shape, but r a r ~ i n g round n type which is long, broad, and'nearly rectangular, with rounded corners, rather wider a t the foot than the 1ie:td and with a slight inflexion of the sides ; a t tlie head the outline often beconles indistinct ; a fairly typical length of aperture would be -35--4 mm., and breadth '25--27 mm.

O ~ c i a small, inconspicuous swellings a t the head of the zocecium;