FAUNA OF THE GOSAU FORMATION. 



701 



having disappeared before the bone came into my possession. It is 

 impossible from this slender evidence to determine the affinities of 

 this animal. 



Orxithocheirf/s Bttnzeli, Seeley. 



The remains of Ornithosanrians are unsatisfactory, being, for the 

 most part, either small portions of shafts of bones, or else bones 

 which have been greatly crushed. The fragments of phalangeal 

 bones throw no light on the structure of the animals to which they 

 belong, and give no clue to specific characters. The bone-tissue, how- 

 ever, is somewhat thicker than in English specimens ; and! have no 

 doubt the fragments belong to a peculiar species. There is an in- 

 teresting crushed proximal end of a humerus, showing the form of 

 the head, the immense radial crest, and the ulnar expansion of the 

 bone at the humeral articulation : and this, with some other frag- 

 ments, characterized by thin texture of the bone, may, perhaps, 

 indicate a second species. But although of great local interest as 

 demonstrating the presence of these animals in a period of time 

 in which they were so plentiful in England, these fragments are 

 of no importance to the anatomist. The only specimen of import- 

 ance is the articular end of the lower jaw, already described by 

 Biinzel (pL vi. figs. 6, 7). This bone is obliquely fractured just 

 in front of the articular end, and shows the articular surface 

 and the characteristic keel beyond it. The length of the fragment 

 is 31 millim. The bone is compressed from side to side ; and the 

 sides converge downward into a narrow rounded ridge. The ex- 

 ternal surface is flattened like the internal surface, which latter 

 shows a suture with very irregular margin, nearly parallel to the 

 base, and near to it, indicating that the articular bone was re- 

 ceived into the angular bone. The area in front of the articula- 

 tion contracts from side to side, and is rounded ; but on the inner 

 margin there is a large pit partly fractured through, indicating a 

 pneumatic foramen. The articular surface is transversely ovate in 

 area, with a median ridge running obliquely backwards and outwards 

 from the hind margin of this foramen. This divides the articular 

 surface into a triangular concave area in front and towards the 

 outer side, and a posterior groove which is best developed towards 

 the inner side of the jaw. This articulation perceptibly widens the 

 bone at each side. Its width is 13 millim., its length 8 millim. 

 Behind the articulation there is no defining border, like the sharp 

 elevated ridge in front, but the surface is flattened, with the sides 

 slightly converging till they terminate in the rounded extremity. 

 This posterior area is directed obliquely downwards to the base of 

 the bone. The inner half of its surface consists of a pneumatic 

 foramen, which is 13 millim. long, and reaches forwards to the 

 posterior articular groove. This jaw seems to be well distinguished 

 from the species already described. 



