Prof. Owen on Reptilian Remains from South Africa. 79 



females ; or of their being individuals which had lost their tusks 

 without power of replacing them, as the known structure of the true 

 Dicynodons indicates. But there are characters of the zygomatic 

 arches and temporal fossa? which differentiate the toothless skulls 

 sufficiently to justify their provisional reference to a distinct subgenus. 



Hyoid apparatus of Oudenodon. — Beneath one of the skulls, 

 and imbedded in the matrix between the mandibular rami, were the 

 following elements of the hyoid apparatus : — basi-hyal, cerato-hyals, 

 thyro-hyals (or hypo-branchials), cerato-branchials, and uro-hyal. 



The cerato-hyals are long, subcompressed, expanded at both ends ; 

 the thyro-hyals shorter and more slender ; the cerato-branchials 

 with a sigmoid flexure ; the uro-hyal symmetrical, broad, flat, semi- 

 circular, with a production like a stem from the middle of the straight 

 anterior margin. This apparatus shows the complexity by which 

 the hyoid in Lizards and Chelonians differs from the hyoid in Cro- 

 codiles, and combines Chelonian with Lacertian characters. Trans- 

 mitted by Mr. Bain from South Africa. 



Dicynodon tigriceps. — Pelvis : ilium, ischium, and pubis coalesced 

 to form an c os innominatum,' w T ith the suture at the symphysis 

 obliterated. At least five sacral vertebrae ; the first wdth broad, 

 thick, triangular, terminally expanded pleurapophyses. The strong, 

 straight, trihedral ilium overlies the above sacral rib, and extends 

 forward to overlie also the last long and slender rib of the free 

 trunk (thoracic) vertebra?. There are no lumbar vertebra?. 



Pubis very thick, strong, with a broad anterior convexity resem- 

 bling that of the Monitor in its internal perforation and external 

 apophysis ; ischium receiving the abutment of the last two pairs of 

 sacral vertebra?. 



The form of the anterior aperture of the pelvis is oval, with the 

 sides broken by a slight angle at the middle, and the small end 

 encroached upon by the slight angular prominence of the symphysis 

 pubis. The long diameter is 11 inches (from the fore-end of the 

 first sacral vertebra), the transverse diameter is 10 inches. The fore- 

 half of this aperture is bounded by the first sacral vertebra exclusively, 

 at the middle by its centrum, at the sides by its ribs ; the hind-half 

 of the aperture is bounded by the pubic bones. From the penulti- 

 mate sacral vertebra to the symphysis pubis it measures 5 inches. 



The outlet of the pelvis is of a semielliptic form, 9 inches in 

 transverse, and 4 inches in the opposite diameter. Original trans- 

 mitted by Mr. Bain from East Brink River, South Africa. 



Crocodilia (?). Genus Massospondylus, Ow. (Gr. fiuaaiov, 

 longer; <nrdrlv\os, vertebra). — The author exhibited diagrams, and 

 pointed out the characters on which he had founded (in the Cata- 

 logue of Fossil Remains of the Museum of the College of Surgeons) 

 the genus Massospondylus, exemplified by the M. carinatus. 



Genus Pachyspondylus, Ow. (Gr. Ttayvs, thick ; onovcvXos, ver- 

 tebra). — The fossils exemplifying this genus form part of the same 

 collection, obtained by Messrs. Orpen from sandstones of the Dra- 

 kenberg range of hills, South Africa, and presented to the College 

 of Surgeons. 



