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Show 171 KB. S. A. BOULENGER ON THE [^Pr- x^' Procolophon*, differing, however, in the molar teeth being wider still, in this respect agreeing with Diadectes and Empedias, as figured by Cope t. THE VERTEBRAL COLUMN. I have very little to add to OUT previous knowledge of the vertebral column. Having had gutta-percha and wax impressions made of the specimen described by Huxley, and also from examination of the type specimen, I can state that intercentra were absent between the dorsal vertebrae, that these were rather strongly biconcave, and that transverse processes did not exist. The number of presacral vertebra? in specimen B was twenty. The long and slender presacral ribs were but slightly thickened at the base. The length of the tail is still unknown ; but it was probably not much longer than in the type specimen figured by Mantell. THE PECTORAL ARCH. This was inserted immediately behind the skull, as in the Stegocephala, Pariosaurus, Procolophon, and Sclerosaurus %. Although the fossils at hand do not show the characteristic T-shaped interclavicle, I have no doubt the shoulder-girdle agreed essentially with that of Procolophon. This part of the skeleton is best shown by Huxley's specimen. But for the anterior expansion of the glenoid cavity, which seems to me doubtful, the scapula has left a cast which agrees well with Huxley's restoration. But the latter is to a great extent fanciful as regards the coracoid, part of which, it is true, is indicated in the figure § by a dotted line. The large fenestra does not appear to have existed, its supposed presence being due to matrix which, I think, could be easily removed were it not that the historical interest attaching to the specimen precludes its further development. The important point, overlooked by Huxley, is the presence of a straight transverse suture, extending from the glenoid cavity, which divides the bone into two, the prsecoracoid and the coracoid, the former being only a trifle shorter than the latter. Cleithra were certainly not present. THE PELVIC ARCH. This has been described very shortly by Huxley, and the outline figure given by him indicates a very Lacertilian state of things. I agree with his representation of the ilium, but I am convinced that the supposed impressions of the pubis and ischium * Cf. PI. X X X I . fig. 3. t Proc. Amer. Philos. Soc. xix. 1881, pi. v. X The restorations of Sclerosaurus by von Huene, Geol. Pal. Abb. x. 1902, p. 29, and of Pariosaurus by Broom, Ann. S. Afr. Mus. iv. 1903, pi. xvi., appear to m e both incorrect in representing these reptiles with a distinct neck. Fossils in situ show the clavicular arch to have been under the anteriormost cervical vertebra?. These reptiles had no more neck than a Salamander. § Loc. cit. p. 78. |
