1904.] TRIASSIC REPTILE TELERPETON ELGINEXSE. 475 



ai-e a fallacy, as I have satisfied myself that the two bones have 

 left pei'fectly defined impressions on the counterpart of the fossil 

 from which Huxley di-ew up his desciiption and diagram. A 

 figu.ve 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 Ti-iassic Rhynchocephalians, 

 Plesiosaurians, and Ichthyosaurians, the pubis and ischium were 

 plate- like ; these two bones were in contact with each othei" and 

 with their fellows, wliilst the formei* was piei'ced by a foramen 

 neai" the an tei'o- external side, this foramen appearing as a knob- 

 like 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 wei-e thickened on their acetabular bordei- and at 

 the symphysis ; the outer border of the ischium was strongly 

 notched, the gi-eatest width being at the line of the acetabulum : 

 the length of the ischium was once and thi-ee-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 %. 



The position of the ilium on Huxley's specimen shows it to have 

 slanted slightly backwai-ds f I'om the saci-um to the acetabulum, and 

 that of the pubis and ischium also indicates the iliosacral attach- 

 ment to have been prteacetabular, although to a but slight extent 

 by no means comparable to that i-eached 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. Hull 

 has succeeded in exposing the outline of the right humerus. This, 

 in its widely expanded pi-oximal end and naiTOW shaft, is seen to 

 be extremely similai- 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 cleai-ly on the gvitta-percha impressions which have now 

 been taken. The phalangeal formvila is, therefore, 2.3.4.5.3. 



* PI. XXXII. 



t Cf. Broom, Rec. Albany Mus. i. 1903, p. 22, pi. i. iig. 5. 



X Cf. Mantell, I. 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 pr;eacetabular 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 " prKacetabular," and lead to the Mammalia, and all other orders of Reptiles 

 are " postacetabular," or show a tendency in this direction. This, in my opinion, 

 speaks against the attempt which has recently been made by Osborn (Mem. Am. 

 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. 



II Cf. Seeley, I. c. pi. ix. 



