VERTEBRATES. 23 



wanting, but enough of it remains to show that it was strongly 

 compressed, with a lenticular section and cutting edges, was 

 marked with fine, sharp striae near the base, and smooth above. 

 The lateral denticles are two in number on either side, rela- 

 tively large, and differing but little in size. Like the median 

 cone they are striated below, smooth, compressed and ancipital 

 above. The outer pair must have been nearly half the length 

 of the middle cone. The base of the tooth is of moderate 

 thickness, in width about equal to twice the length of the 

 larger lateral denticles. 



In general aspect, the relative breadth and height, and the number and size 

 of the lateral denticles, this species bears considerable resemblance to C. mira- 

 bilis, Ag. (Pois. Foss., Vol. 3,jp. 197, Atlas, Vol. 3, Tab. 22 I, fig. 9-13), but 

 that species is more generally and strongly striated, and the median cone has a 

 circular section throughout. 



Figure 5. Anterior face of broken tooth, with section of median cone. 



Formation and locality: Coal Measures, Sugar creek, Sangamon county, Illi- 

 nois. 



Cladodus stenopus, N. and W. 



PL 1, Fig. 4, 4 a. 



Teeth of medium size ; breadth of base slightly greater than 

 height; base laterally elongated and narrow, semi-elliptical, 

 beveled to an edge behind, curved under before, where it has a 

 broad but shallow sinus ; median cone conical, with an expand- 

 ed base, slightly curved backward, compressed, both anterior 

 and posterior surfaces flattened, and very finely and uniformly 

 striated-; lateral denticles 6-7 on either side, exterior pair 

 much the largest, intermediate ones, sub-equal. 



There are no entire specimens of this species in the collection, the denticles 

 being all more or less truncated. The narrow, smooth, broadly-sinused base, 

 and the median cone, with both anterior and posterior surfaces flattened, and 

 yet not acutely angled, except near the point, render it distinguishable at a 

 glance, from the species associated with it. In size and surface markings it is 



