150 



Baron F. Nopcsa — British Dinosaurs- 



The slender pubis of St. priscus (Fig. 8a) is a very remarkable 

 element. Its anterior branch, corresponding functionally, though not 

 in its origin, to the processus pectinealis of birds, and therefore 

 appropriately named processus pseudopectinealis, is badly fractured ; 

 but from the part preserved we may infer that it had a long, slender, 

 blade-like shape, as in 0. armatus (Fig. 8a), but was more inclined 

 downwards than in this genus. The foramen obturatorium is open 

 towards the suture of the ischium, as in St. unqulatus and Omosaurus. 

 The acetabulum is but feebly marked and disfigured by crushing ; the 

 post-acetabular part of the pubis is a slender rod-like bone, of -which 

 the middle part is wanting. The distal end of the pubis is thickened 

 and covered with rugosities, which form, where the pubis originally 

 met the ischium, a horseshoe-shaped area. This area and a strong 



Fig. 8. a. Ischium and pubis of 0. armatus. b. The same of St. priscus. 



projecting rugosity on the inferior surface of the shaft of the pubis 

 were both well figured by F. von Huene in the Ceniralblatt fur 

 Mineralogie, etc. (1902), when discussing the Cambridge specimen 

 of St. priscus. 



In consequence of its slender rod-like shape, the pubis of St. priscus 

 resembles the same bone in 0. armatus more than in Stegosaurus, but 

 the rugosity on the shaft is wanting in 0. armatus. A slender rod- 

 like post-pubis is present also in 0. Lennieri. Some evidence that 

 the pubis of St. priscus was more slender than the same bone in 

 0. armatus is afforded by the shape of the well-preserved ischium. 

 This bone (Fig. 8b) is a long, triangular, flat element, showing 

 a concave surface only at the acetabulum and tapering in the usual 

 Omosaurus-likc manner towards its distal end, which is triangular 

 in section and is applied closely to the pubis. Further forwards 



