262 



PKOFo OWEN ON THE OEDEK THEEIODONTIA, 



racter ; and 'with Titanosuclius, for the same reason, may be cited 

 Kutorga's Britliopus and Orthopus, from Russian Permian, V. Meyer's 

 Urosaurus, Fischer's Rhopalodon, Eichwald's Deuterosaurus, and 

 Twelvetrees's Cliorhizodon, from the same zone and locality ; to the 

 Theriodontia belongs also Bailiygnathus from the Trias of " Prince 

 Edward's Island," North America*. 



To add to this series of Theriodont genera, and, seemingly, to the 

 " Mononarial " section, I now submit to the Society evidence of 

 another genus, JElurosaurus, exemplifying in a clear manner the 

 typical Theriodont characters, under modifications generically distinct 

 from those of the specimens above cited. 



It is a skull, including both upper and lower jaws, with the orbits, 

 obtained by Mr. Thos. Bain from the Trias of Gough, in the Karoo 

 district of South Africa, and in the usual petrified condition of the 

 fossils of that formation and locality. The postorbital part of the 

 skull is broken away, and the border of the nostril has been slightly 

 fractured ; but the rest of the specimen, with the dentition, is 

 instructively preserved. 



The nostril (PI. IX. figs. 1 & 2, n) is terminal and vertical, and 

 shows no part of a septum ; in shape it is a full transverse ellipse ; 

 what remains of the outlet yields in breadth 13 millim., in depth 

 9 millim. Each orbit (ib. ib. o) gives a full obliquely vertical 

 ellipse, 25 millim. by 20 millim. The facial part of the skull 

 extends two and a half times the fore-and-aft diameter of the orbit 

 in advance of that cavity. The "breadth of the upper jaw a little 

 behind the nostril is 26 millim., and gradually increases to 35 

 millim. near the orbits. The upper surface of the antorbital part 

 of the skull is moderately convex ; the sides are less convex, but not 

 flat ; the vertical extent of the upper jaw at the middle of the molar 

 series is 34 millim., and decreases to 20 millim. above the incisors. 



The skull has been subject to slight distortion ; but as this has 

 been effected without fracture, it may be concluded to have been 

 due to forces operating on the matrix after petrifaction, and when 

 the fossil was so encased as to be equally supported on every side 

 during the movements of the bed, such partial pressure having 

 chiefly affected the left orbit (ib. fig. 3, o) and a small part of the 

 same side of the skull in advance of it. Erom the degree in which 

 the sutures are obliterated, I conclude it to have come from a full- 

 grown and probably old individual, the state of the dentition sup- 

 porting that inference. 



The premaxillo-maxillary alveolar border, as it recedes from 

 below the nostril, follows a slightly sinuous course, concave above 

 the incisors, convex above the canine and the molars; thence 

 straight to beneath the orbit. 



The mandible is preserved, with the mouth close-shut ; and the 

 mandibular teeth are hidden by the overlapping ones of the upper 

 jaw, requiring the sections made in two places for exposure (ib. 

 fig. 3, c ). The symphysis mandibulje (ib. fig. 3, s) is 27 millim. in 

 depth and 20 millim. in breadth where it is crossed by the upper 

 * Quart. Journ. Geol. Soc. vol. xxxii. p. 352, 1876. 



