150 NEW YORK STATE MUSEUM 



adapted for subsistence on soft tissues, and were probably predaceous 

 creatures. Mylostoma and Dinichthys furnish examples of corresponding 

 adaptations amongst Arthrodires, and we have already seen that analogous 

 changes are sustained amongst Dipnoans of the present clay. 



The mandibles of Mylostoma would seem to have retained with great 

 persistency typical Dipnoan conditions. Not only do the dental plates 

 portray what may fairly be called a Ceratodontlike configuration, but they 



Fig. 31 Upper dentition of Mylostoma variabile Newberry, based upon a single, nearly complete example from the 



Cleveland shale near Cleveland, O. Nat. size 



are more sharply demarcated from the supporting splenial than in other 

 Arthrodires. And although marginal serrations have disappeared, the 

 divided ridge which occurs close to the inner margin is perhaps to be 

 regarded as a relic of one of the most persistent features of Dipnoan denti- 

 tion. As for the upper dental plates, had they always been found in the 

 detached condition, and were we ignorant of their association with typical 

 Arthrodiran mandibles, they would be unhesitatingly identified with the 

 Ctenodipterine order of Dipnoans. That these plates were supported in 

 cartilage forming the roof of the month is perfectly evident from their rugose, 

 slightly hollowed upper surface, and outwardly beveled edges ; and the pos- 

 terior contour of the hinder pair renders it extremely probable, at least, 



