110 PROCEEDINGS OF THE ACADEMY OF [1883. 



Measurements. m. 



Elevation of first crest at middle, . . '0095 



Elevation of second crest at middle, . . '0065 



Length of a tooth of second crest, . . *0020 



The peculiarities of this tooth suggest that the genus Gnathor- 

 hiza Cope (Proceedings Amer. Philos. Soc, 1882, p. 629) is 

 Dipnoan, and allied to Gtenodus. 



Ctenodus vabaseusis sp. nov. 



This fine species is represented by an almost perfect tooth. 

 It is allied to the G. fossatus Cope, but is wider, and the crests 

 do not radiate so equally, but are chiefly directed in one direction 

 as in most species of the genus. The C gurleianus and G, 

 pusillus are at once distinguished by the small number of crests, 

 while the G. periprion and G. dialophus have a larger number of 

 crests, and are otherwise different. G. porrectus differs less from 

 it, but has only five \ crests, while the C. vabasensis has six \. 

 The \ represents the small posterior (?) crest, which is double. 

 This, with the next one, is directed slightly posteriorly; the 

 fifth is at right-angles to the long axis, and the anterior four 

 extend more or less forwards. They are serrate nearly to their 

 bases, but the teeth are obsolete on their basal halves. The 

 straight part of the internal edge extends as far forwards as the 

 fourth crest, and is continued posteriorly as a short process. No 

 fossae at ends of crests. Superior face of tooth wide, and slightly 

 concave. The anterior parts of the first and second crests are 

 broken away, so that it is impossible to say whether they are 

 produced as in G. porrectus. 



Measurements. M. 



Length to marginal base of second crest, . . '024 



Width at marginal base of second crest, . . "009 



Width at fourth crest, inclusive of apex, . . '015 



Width of posterior side, "010 



Thickness at base of fifth crest, .... '005 



