SUPPLEMENT. 251 



centrum of that specimen is amphiccelous, with a sharp haemal 

 carina, considerable lateral compression, and a highly curved ventral 

 profile. The neck of the animal to which it belonged was evidently 

 much arched ; and from the general characters of the vertebra, and 

 especially the deep median incisions between the zygapophyses, it is 

 probable that it belonged to a Dinosaur allied to the Anchisauridce. 

 This is confirmed by the longitudinal fissure in the centrum, which 

 is probably due to the crushing in of a central cavity. 



Arctosauras osborni, Adams '. 



The type and only described species. Apparently somewhat 

 smaller than Calamospondylus food. 

 Hab. Arctic America. 



R. 1611. Cast of a crushed and imperfect cervical vertebra. The 

 original (fig. 59), which is the type, and is preserved in 

 the Museum of Science and Art, Dublin, was obtained 

 from beds of unknown age at Eendezvous Mountain, at 

 the north end of Bathurst Island. It is described and 

 figured by Adams in the Proc. E. Irish Academy, ser. 2, 

 vol. ii. p. 177 et seq. ; and also, by the present writer in 

 the 'Geol. Mag/ dec. iii. vol. vi. pp. 352, 353. The 

 neural spine, the right prezygapophysis, and the costal 

 facets of both sides are wanting ; and a great part of the 

 outer surface of the left side of the centrum is likewise 

 absent. Presented by the Director of the Science and 



Art Museum, Dublin, 1889. 



Suborder ORNITHOPODA {supra, i. p. 175). 



Family STEGOSAUR1TLE. 

 = Omos atjrid^e {supra, i. p. 176). 



Genus STEGOSAURTJS, Marsh 2 . 



Syn. Omosaurus, Owen (supra, i. p. 177). Preoccupied by Leidy, 1856. 



The absence of an inner trochanter in the American forms is not 

 regarded by Marsh (' Amer. Journ.' ser. 3, vol. xxxvii. p. 327) as 

 a generic distinction. 



1 Proc. E. Irish Academy, ser. 2, vol. ii. p. 177 (1875). 



2 Amer. Journ. ser. 3, vol. xiv. p. 513 (1877). 



