252 KANSAS UNIVERSITY SCIENCE BULLETIN. 



spines showing different characters might very easily occur 

 in various portions of the vertebral column. 

 Measurements of vertebrae : 



Length of centrum 2.5 cm. 



Width of centrum 3.2 



Height of vertebrae to tip of spine 13.4 



Thickness of top of spine 3 



Broili (Monatsb. d. Deutsch, Geol. Gesell., Bd. 60, Texttafel 

 p. 236, fig. 2) has figured in Eryops megacephalus a peculiar 

 element which he has identified as the sacral rib, having found 

 it in place with a sacral vertebra. There is no doubt that the 

 present element (plate LIV, figs. 3 and 4) is the same as he 

 has figured. Its interpretation as a sacral rib is somewhat 

 surprising on account of the extreme thinness of the bone. It 

 thins out to less than a millimeter on one edge. Its location 

 any other place in the iskeleton is, however, doubtful. 



The element has a broad base as if for attachment suturally 

 with the vertebral transverse process. The base of the speci- 

 men has been broken transversely and only a portion of the 

 suture remains. The bone is flat immediately from the base 

 and is greatly expanded and thinned distally. It is, for the 

 most part, smooth, though there is a small roughened place on 

 the dorsal ( ?) surface. The ventral ( ?) surface is marked by 

 a depression which runs the entire length of the bone. The 

 distal end is lost. 



Measurements of sacral rib: 



Actual length of specimen 90 mm. 



Width at distal end 62 



Width at middle of blade 32 



Width at inner end 55 



Eryops willistoni differs from E. ferricolus Cope in the 

 absence of a raised rim to the orbits. From E. erythrolithicus 

 Cope it differs in the non-bifurcation of the neural spines. 

 This last is not a well-known species and may be synonymous 

 with E. megacephalus. E. reticulatiis is a small species, from 

 which E. willistoni differs in the character of the cranial sculp- 

 ture. It is distinct from E. latus Case on account of the di- 

 mensions of the scapula and the cleithrum. E. megacephalus 

 also shows characters which are divergent from those of the 

 present species. These are the shape and structure of the 

 mandible and its ornamentation, the form of the humerus and 



