DEVONIC FISHES OF THE NEW YORK FORMATIONS 97 



Strongly developed, supporting the dental plate sensii strido in front, and 

 being articulated posteriorly with the cranium by cartilage, as in Neocera- 

 todus. But one interpretation can be given of the conspicuous groove 

 which extends forwards along the inferior border of the splenial, passing 

 underneath and to the inner side of the dental plate proper, and terminat- 

 ing near the symphysis. In it were lodged remnants of the Meckelian 

 cartilage, precisely as in the living Protopterus. Intermandibular teeth 

 have not been definitely proved to occur, although their presence would be 

 in strict accord with embryological evidence, and the appearance of certain 

 specimens has led some investigators to suspect that such teeth were 

 developed ; moreover, in Coccosteus, Diplognathus etc., we are confronted 

 with a denticulated symphysial margin, the significance of which has not 

 been explained. Finally, it should be noted that an approach to the 

 Dinichthyid form of mandible is made even amongst Ctenodipterines,' and 

 some of these also develop cutting edges, asinSagenodus pertenuis," 

 for example. 



Dentition of Mylostoma and Neoceratodus compared. Our knowledge of 

 Mylostoma received important additions a few years ago as the result of 

 Dr Bashford Dean's investigation of the type species.^ Since then, how- 

 ever, fresh material has been brought to light which shows that this author 

 was not entirely successful in determining the relations of the palato- 

 pterygoid dental plates in the unique specimen studied by him. Their 

 true disposition has recently been ascertained beyond doubt to be as rep- 

 resented in the accompanying text figure i8, a similar arrangement holding 

 true also for Dinomylostoma, and, interestingly enough, being repeated in 

 early stages of Neoceratodus. This we have already alluded to in a pre- 

 ceding paragraph, by saying that Neoceratodus passes through a Mylo- 

 stomid stage. One can hardly fail to appreciate the significance of this 



'Atthey, T. On Ctenodus obliquus, etc. Mag. Nat. Hist. Ann. ser. 4, 1875. 15:309, 

 pi. 19, fig. 2. 



2 Eastman, C. R. A Peculiar Modification amongst Permian Dipnoans. Am. Nat. 



1904. 37:493-95- 



3Dean, B. Palaeontological Notes. N. Y. Acad. Sci. Mem. T901. 2: 101-9. 



