262 PALAEONTOLOGY OF ILLINOIS. 



continuous, strongly marked ridge projecting downward and slightly 

 outward, or sometimes more or less distinctly divided into two lobes by 

 a faint median constriction in the inner side, along which it is always 

 sharply beveled toward the concavity of the root, from the body of 

 ■which it is more or less distinctly defined laterally ; posteriorly the base 

 is gently rounded, aud surmounted by a well marked ridge, which 

 makes an abrupt descent to the posterior .margin, with which it is 

 parallel, and separated from the crown by a shallow channel; surfaces 

 irregularly roughened and pitted. Crown slightly constricted along the 

 basal line in front, the sinuosity of the usually deep basal region extend- 

 ing up into the median cone as a faint depression, while the enamel of 

 the inner face terminates in a faint line; mediau cone strong, laterally 

 deflected and generally strongly recurved, rapidly tapering to an 

 obtusely rounded point, compressed in front aud broadly rounded 

 behind, with sharp lateral edges; lateral denticles four on either 

 extremity, alternating jLore or less irregularly in size, in shape resem- 

 bling the median cone ; the exterior pair relatively strong and outwardly 

 and posteriorly curved ; the outer basal line is marked by .irregularly 

 disposed tuberclesor processes, which are more markedly developed in 

 the lateral regions, and sometimes flank the exterior denticles ; besides 

 the latter, the lateral denticles are ornamented with one or two, perhaps 

 rarely more, sharp costse, while the median cusp in some individuals 

 bears five or six similar costal, irregularly spaced, implanted or rarely 

 bifurcated descending, and seldom reaching two-thirds the distance 

 towards the apex; the cost* of the inner face are apparently equally 

 irregularly developed aud more delicate, aud usually obsolete in the 

 lateral denticles. A well proportioned specimen of medium size meas- 

 ures in greatest lateral diameter of base .38 inch, greatest hight of 

 tooth .32. 



Although the general features presented by the teeth here recognized 

 are quite persistent, a considerable range of variation occurs in indi- 

 viduals, rendering it difficult in many instances to determine their 

 identity, especially in worn and otherwise mutilated or abnormally 

 developed specimens. In some respects the form bears intimate com- 

 parison wth C. Wachsmuthi, as especially noticeable in the base, which 

 is almost the exact likeness of the latter form ; the coronal region, on the 

 other hand, presents an equally striking resemblance to G. Springeri, 

 ■with which it is associated, and from which it is recoguized chiefly by 

 the fewer accessory processes and costae in the outer aspect, and its 

 dwarfish and less symmetrical proportions. It is possible that it may 

 prove to belong to the former of the above named forms ; but no exactly 

 similar individuals are as yet known from the horizon in which G. 

 Wachsmuthi occurs, while the characters which serve to distinguish the 



