GO PALEONTOLOGY OF OHIO. 



sharp radiating ridges, which terminate above in numerous compressed, 

 acute denticles ; the furrows between the ridges being pitted to receive 

 corresponding denticles of the opposite teeth. These ridges and furrows 

 varj^ much in length, so that one end of the tooth forms a long pointed 

 triangle, and at the opposite extremity the crown is rounded and the 

 base projects in a depressed and flattened point. 



In o-eneral form and marking this tooth bears considerable resemblance 

 to that of Ct. oUiquus of the Northumberland coal-fields, England, but the 

 ridges are more numerous and much narrower. From the larger species 

 of Ctenodus found in England, Ct. tuberculatus, etc., it will be at once 

 distinguished by the tan-like radiation of its ridges, which all centre at 

 the most prominent point of the erow^n. When in its perfect condition 

 this is the most elegant species of the genus yet discovered. It is charac- 

 terized by a remarkable exactness of form and sculpture. The internal 

 margin forms a graceful arch from which the prominent point of the 

 base projects at the end of the tooth where the ridges are shortest. The 

 denticles which crown the ridges are much com»pressed, wQrj sharp, and 

 somewhat curved outward. 



Fig. 15 represents a tooth of the lower jaw seen from above ; 15a, one 

 of the ridges in profile ; 16-, a small, triangular tooth probably from the 

 upper jaw of a smaller individual of the same species. 



In the Report of Prof. E. D. Cope, contained in this volume, will be 

 found a figure and description of a portion of a large ci-anium of what is 

 supposed to be a species of Ctenodus, found at Linton. A more com- 

 plete cranium of the same kind, which I have, is about 8 inches in diam- 

 eter, and the teeth which w^ere once connected with it must have been 

 considerably larger than any yet found at Linton. Prof. Cope calls his 

 species Ct. Ohioensis. Whether it is identical with either of the species 

 I have named from the teeth is not yet know^n. 



Formation and Locality : Coal Measures, Linton, Ohio. 



Cteistodus eeticulatus (n. sp.). 



Teeth of medium size (15 lines long, by 10 lines wide) ; general out- 

 line triangular, the inner margin arched. Crown marked wntli 7 low, 

 radiating ridges, of which the summits form zigzag salient lines. The 

 whole crown of the tooth exhibits a fine reticulated ornamentation, 

 which on the ridges is more or less radiate, and has the appearance of 

 hachures. 



The ( dy specimen of this species 3^et found is too imperfect for figur- 

 ing or full description. The characters given above will, liow3\ er, serve 



