
854 THE AMERICAN NATURALIST. 
Campodus corrugatus (Newberry and Worthen) (Fig. 2). 
The symphysial dentition of this species differs from that of 
C. variabilis in that the individual teeth are much more robust, 
less intimately fused with one another, and less differentiated 
in form from the lateral series; they are also apparently fewer 
in number than in the corresponding series of C. variadclis. 
All these characters point to the conclusion that as between 
the two species the latter is much more highly specialized 
and stands nearer to the line which gave off Edestus and other 
extremely modified cestracionts.! 
The unique specimen of C. corrugatus shown in Fig. 2 
exhibits five very robust teeth, which are recognizable by their 
peculiar form as having pertained to the symphysial series. 
Of how many teeth the entire series was constituted cannot be 
told, but owing to the large size of the teeth it is probable that 
the number was less than in C. variabilis, which has as many 
as thirteen. The apical extremities of the crowns have unfor- 
tunately all been broken away, and the bilateral symmetry of 
the series has been disturbed by mechanical agencies since the 
death of the creature, so that the teeth appear to succeed one 
another in spiral fashion, instead of being arched in a single 
plane. The apical portions of the crowns differ from those of 
C. variabilis, also, in that they are more elevated, and are 
inclined backward at a slight angle. 
The coronal surface of each tooth is marked by a prominent 
transverse crest, from which numerous branches are given off 
approximately at right angles on either side. The anterior 
margins of the crowns are very prominently buttressed, an 
especially large projection occurring in the median line on both 
the anterior and posterior faces. Fig. 2 is photographed from 
a cast of the original specimen, which was obtained from Bates 
and Company's coal mine at Winchester, Illinois. 
1 A detailed account of the dentition of Edestus and related forms is given in 
Bull. Mus. Comp. Zoöl., vol. xl, No. 3, 1902. 
