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Show 1904.] TRIASSIC REPTILE TELERPETON ELGINENSE. 475 are a fallacy, as I have satisfied myself that the two bones have left perfectly defined impressions on the counterpart of the fossil from which Huxley drew up his description and diagram. A figure is given of this impression, or rather of a gutta-percha cast of it*, by which it will be seen that, as we now know to be the case in Procolophon t and in Triassic Rhynchocephalians, Plesiosaurians, and Ichthyosaurians, the pubis and ischium were plate-like; these two bones were in contact with each other and with their fellows, whilst the former was pierced by a foramen near the antero-external side, this foramen appearing as a knoblike elevation of the sandstone on the fossil, and most distinctly on the wax and gutta-percha impressions taken for me by Mr. Hall. Both the bones were thickened on their acetabular border and at the symphysis ; the outer border of the ischium was strongly notched, the greatest width being at the line of the acetabulum : the length of the ischium was once and three-fifths that of the pubis. I may add that a perfectly distinct impression of the pelvis as here described may be seen on the type specimen J. The position of the ilium on Huxley's specimen shows it to have slanted slightly backwards f l-om the sacrum to the acetabulum, and that of the pubis and ischium also indicates the iliosacral attachment to have been praeacetabular, although to a but slight extent by no means comparable to that reached by Pariosaurus §, THE LIMBS. I have a little to add to the information to be gathered from Mantell's and Huxley's descriptions. By careful chiselling of the lower block of specimen B, Mr. Hall has succeeded in exposing the outline of the right humerus. This, in its widely expanded proximal end and narrow shaft, is seen to be extremely similar to that of Procolophon ||. Length 26 millim.; greatest proximal width 14; least width of shaft 3. The femur of the same specimen measures about 30 millim. The hind limb is well shown in specimen A, and the penultimate phalanx of the fifth toe, which has been overlooked by Huxley, appears clearly on the gutta-percha impressions which have now been taken. The phalangeal formula is, therefore, 2.3.4.5.3. * PI. XXXII. t Cf. Broom, Rec. Albany Mus. i. 1903, p. 22, pi. i. fig. 5. X Cf. Mantell, 1. c. pi. iv. fig. 8. The representation of the impression by the lithographer is, however, very incorrect. § Far too little attention has been paid, in defining groups of Reptiles, to what Gadow calls the " crucial features " of the praeacetabular and postacetabular position of the iliosacral connexion (Zeitschr. f. Morphol. iv. 1902, p. 361). Whilst Batrachia generally (excluding the Ecaudata) are indifferent, the Pariosauria and Anomodontia are " praeacetabular," and lead to the Mammalia, and all other orders of Reptiles are " postacetabular," or show a tendency in this direction. This, in m y opinion, speaks against the attempt which has recently been made by Osborn (Mem. A m. Mus. i. 1903, p. 456) to derive the " postacetabular " Chelonia and Plesiosauria from the Cotylosauria and Anomodontia, in his subclass Synapsida, to which I shall again refer later on. || Cf. Seeley, I. c. pi. ix. |
