1882.] 400 [Cope. 



convex. All of them retain the delicate lines and punctse of the inferior 

 surface. The neural spine on the more elongate vertebrae is a rather ele- 

 vated keel, with horizontal superior edge. Its posterior extremity forms a 

 wedge-like zygosphen. The zygantrum is a deep V-shaped cavity, open- 

 ing posteriorly and not roofed over at any point unless for a small part of 

 its fundus. The zygapophyses are well spread, and have horizontal faces. 

 Each of the columns of the diapophysis sends a ridge forwards, which en- 

 close a groove between them. 



Measurements of vertebrce. M. 



Length of atlas below 015 



" " at zygantropophyses 029 



Expanse " " condyloid facets 034 



of centrum atlas behind 0145 - 



Depth of atlas at middle 019 



Length of axis below 015 



" at zygantropophyses 016 



Width of zygosphen above 011 



Expanse of postzygapophyses 024 



"Width of centrum posteriorly * 012 



Depth " " 



Length of centrum of another (No. Ill) 018 



(No. IV) 022 



Expanse of postzygapophyses of do 018 



Length of centrum of No. V .022 



Diameters centrum V anteriorly / '" . „ 



(.transverse 012 



Expanse prezygapophyses 021 



Elevation of neural spine from centrum 011 



r anteroposterior 023 



Diameters centrum No. VI < vertical 011 



' transverse 013 



The vertebras of this species are very much larger than those of the 

 I). salamandr aides, and the diapophyses do not originate so low down on 

 the centrum. Otherwise they are much alike. The cranium of the Illinois 

 species is yet undetermined. 



The D. magnicomis was discovered by W. F. Cummins. 



ACHELOMA. Cope, genus novum. 



Order Rhachitomi ; family Eryopidae,* differing from Eryops in the ab- 

 sence of notch of the posterior border of the skull between the epiotic and 

 quadrate or squamosal bones, and in the absence of condyles of the hu- 

 merus. 



Mandible without angular process. Teeth of the jaws subequal, rather 

 larger anteriorly ; some large ones on the os palatinum at different points 



* American Naturalist, 1882, p. 335. 



