18 • SYSTEMATIC PALEONTOLOGY 



Length centrum lumbar 1 in. 9 lines (43 mm.) 



Width articular face 1 in. 7.5 lines (40 mm.) 



Height 1 in. 6 lines (37 mm.) 



Length diapophysis 3 in. (50 mm.) 



Width neural canal oi ( ^ , . ) 3 lines ( 6 mm.) 



1 Posterior ( ^ ^ 



Whole height of < ^^^^^^^ > 3 in. 8 lines (91 mm.) 



Length diapophysis of ' J 1 in. 6.5 lines (38 mm.) 



This specimen consisted of 2 cervicals, 3 dorsals, and 8 lumbars; the 

 lumbars are characterized by the long spinous transverse processes. 

 Cope says of this species, "■ this is the type of the genus, for in it the 

 peculiar form of the diapophyses extends much farther forward on the 

 series of vertebrae than in any other." Cope^ 1868. 



Occurrence. — Calvert Formation, Charles county near the Patux- 

 ent river. 



Collection. — Philadelphia Academy of Natural Sciences. 



IXACANTHUS ATROPIUS Cope. 



Plate XIII, Figs. 5a, 5b, 6. 



' Priscodelphinns atropitis Cope, 1868, Proc. Acad. Nat. Sci. Phila., voL xx, pp. 187, 



188. 

 Priscodelphinns atropitis Leidy, 1869, Jour. Acad. Nat. Sci. Phila., 3nd ser., vol. vii, 



p. 433 (mention only). 

 Belosphys atropius Cope, 187.5, Proc. Amer. Philos. Soc, vol. xiv, p. 363. 

 Ixacanthus atropius Cope, 1890, Amer. Nat., vol. xxiv, p. 614. 



Description. — " The diapophysis of the caudal is short and spinous, 

 as in the last species (P. spinosus), and the last lumbar has had a 

 nearly similar process. The centra of all are very slightly compressed 

 and constricted medially. The dorsals are broadly rounded in section 

 without inferior carina; on the last lumbar the lateral face below be- 

 comes, as in other species, slightly concave." 



" Length of dorsal (1) 3 in. 2 lines (54 mm.) 



Width articular face 1 in. 11.5 lines (48 mm.) 



Depth articular face 1 in. 7 lines (39 mm.) 



Height neural canal (2) 9.7 lines (44.4 mm.) 



Length diapophysis (1) 1 in. 4 lines ^33 mm.)" 



Cope. 1868. 



