DJCYNODONTID^). 33 



47098. The imperfect posterior portion of a small cranium ; from 

 the Karoo system of the Cape Colony. The specimen is 

 broken off near the anterior border of the orbits. 



Presented by A. G. Bain, Esq., 1853. 



Genus PTYCHOSIAGUM, Lydekker 1 . 

 Syn. Ptychognathus, Owen 2 . 



Cranium, so to speak, bent upon itself, with more or less strongly 

 marked angles at the junction of the occipital with the parieto- 

 frontal plane, and of the latter with the naso-premaxillary plane. 

 Supratemporal f ossae wider than long ; preorbital region much elon- 

 gated, and the facial portion of the long premaxillse with strongly 

 marked lateral ridges, bordering a flat anterior surface ; nares far 

 behind muzzle ; nasals short ; orbits lateral ; supraoccipital with 

 only a very narrow bar over foramen magnum, above which is a 

 notch for the reception of a descending process of the interparietal 

 (fig. 6); inferior aspect of mandibular symphysis flattened, with 

 lateral angulation. 



The posterior extremities of the tusks are situated immediately 

 below the nares ; and the tusks extend downwards and forwards 

 parallel with the naso-premaxillary plane, not leaving the sockets 

 until they have passed beyond the level of the posterior end of the 

 mandibular symphysis. 



In some cases at least (P. orientale) the centra of the dorsal 

 vertebra? long and much less deeply cupped than in Dicynodon. 

 Scapula (when known) with the acromial process separated only by 

 a groove on the ventral aspect from the glenoidal region, and a 

 short notch-like emargination on the preaxial border, which above 

 this notch is twisted towards the dorsal aspect. 



]S"one of the species attained dimensions at all approaching those 

 reached by the larger species of Dicynodon and Udenodon. 



Specimens of the pectoral girdle probably belonging to this genus 

 are noticed on pages 52 and 53. 



1 In Nicholson and Lydekker's ' Manual of Palaeontology,' 3rd ed. toI. ii. 

 p. 1063 (1889). 



2 Quart. Journ. Geol. Soc. vol. xvi. p. 49 (1860). — Preoccupied by Stimpson, 

 Proc ? Ac. Nat. Sci. Philad. 1858, p. 104, for a Crustacean genus. 



PART IV. 



