1882.] 400 [Cope. 



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

 surface. The neural spine on the more elongate vertebra; 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, wliich en- 

 close a groove between them. 



Measurements of vertehne. 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 OIG 



Width of zygosphen above Oil 



Expanse of postzygapophyses 024 



Width of centrum posteriorly 013 



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 



^. _ . , r vertical 01?> 



Diameters centrum V anteriorly i. p..„ 



•' (. transverse 012 



Expanse prezygapophyses .021 



Elevation of neural spine from centrum Oil 



f anteroposterior 02o 



Diameters centrum No. VI < vertical Oil 



' transverse 013 



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



D. salamandroides, and the diapophyses do not originate so low down on 



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



species is yet undetermined. 



The Z>. magnicornis was discovered by W. F. Cummins. 



ACHELOMA. Cope, genus novum. 



Order Rhachitomi ; family Eryopidae,* diflering 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. 33.5. 



