60 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 

 vary 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 

 bkse projects in a depressed and flattened point. 



In general form and marking this tooth bears considerable resemblance 

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

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

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

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

 the most prominent point of the crown. 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 compressed, very 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 Eeport of Prof. E. D. Cope, contained in this volume, will be 

 found a figure and description of a portion of a large cranium of what is 

 supposed to be a species of Gtenodus, 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 were 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 known. 



formation and Locality : Coal Measures, Linton, Oliio. 



Gtenodus eeticulatus (n. sp.). 



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

 line triangular, the inner margin arched. Crown marked with 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 loss radiate, and has the appearance of 

 /lachures. 



The r .ly specimen of this species yet found is too imperfect for figur- 

 ing or lull description. The characters given above will, however, serve 



