DEVONIC FISHES OF THE NEW YORK FORMATIONS 6 1 



The relations of this species have been commonly supposed to be with 

 Cladodus, rather than with Diplodus, but recent discoveries of more perfect 

 examples which display the characters of the root, in this and other species, 

 leave no doubt as to the Pleuracanthid nature of these teeth. An illustra- 

 tion is given in the accompanying plates of one of the most perfect speci- 

 mens of P. p o 1 i t u s that has yet been obtained. The original is preserved 

 in the Museum of Comparative Zoology at Cambridge, Mass. 



Formation and locali|:y. Cleveland shale (Upper Devonic) ; Ohio. 



Family pladodontidae 

 An indefinable family, apparently closely related to the Pleuracanthidae. 



Genus cladodus Agassiz 

 This typically Carbonic genus occurs sparingly in the Neodevonic, 

 but only two instances are known of its occurrence in the Mesodevonic, the 

 species immediately to be described being found in the Columbus limestone 

 of Ohio, and the next following from the Hamilton of Milwaukee, Wis. It 

 is quite possible that some detached teeth of similar nature which range 

 upward into the Carbonic belong in reality to Pleuracanthid sharks, their 

 origin being traceable to forms like Protodus and Doliodus in the Lower 

 Devonic. There are strong reasons for believing that the teeth of Lower 

 Carbonic Cladodonts belonged to spineless sharks, and until recently it was 

 supposed that the Devonic Cladoselache was also unarmed. 



Cladodus prototypus sp. nov. 



Plate I, figure 15 



Founded upon a single robust tooth, the crown consisting of a stout 

 erect median cone and five lateral denticles on either side, not much com- 

 pressed, and all delicately striated. The outer pair of lateral denticles is 

 much the largest, and nearly circular in cross-section. The median cone is 

 elliptical in transverse section, slightly recurved, without sharp lateral edges, 

 and very wide across the base. Its total hight, when complete, is estimated 

 to have been about 3 cm. 



The general appearance of this tooth is suggestive of Cladodus 



