DEVONIC FISHES OF THE NEW YORK FORMATIONS 171 



degeneration, the climax of which is reached by the modern Polyodontidae 

 and Acipenseridae. 



Family palaeoniscida-e 



Primitive Chondrostei with fusiform bodies, short dorsal and anal fins, 

 and usually with a complete investment of articulating, rhombic, rarely 

 cycloid, ganoid scales. Fulcra generally present at the bases of the median 

 fins, and especially along the dorsal border of the upper caudal lobe. Ribs 

 are not known to be present. Skull invested by a very complete series of 

 paired dermal bones, which in number and disposition conform to the nor- 

 mal Teleostome type. The secondary upper jaw includes both premaxillae 

 and large maxillae ; and, as a rule, both the dentary and splenial bones of 

 the lower jaw are dentigerous. Except for the absence of an interoper- 

 culum, the opercular series of bones is complete, including numerous 

 branchiostegal rays. There is a single small median jugular plate [Bridge, 

 loc. cit. p. 486]. 



The earliest representative of this family, and of Sturgeons generally, 

 is the genus Cheirolepis, which is remarkable for the very small size of its 

 scales. The typical species, C. trailli, occurs in the Old Red Sandstone 

 of northern Scotland, and another well preserved form, described by Whit- 

 eaves as C. canadensis, is known from the Upper Devonic of the 

 Province of Quebec. Aside from the Canadian form, no completely pre- 

 served individuals are known from the Devonic rocks of this continent, 

 although three species have been founded upon portions of the squamation. 

 These latter have been doubtfully assigned to the genus Palaeoniscus, and ■ 

 are named as follows: P. antiquus and P. reticulatus Williams,' 

 and P. devonic us Clarke.' The two first named are from the Portage 

 beds near Buffalo, N. Y., and the last named, much better preserved than 

 the others, is from the Rhinestreet (Portage) beds of Sparta, N. Y. The 

 scale characters of the Portage species point to an association with the 

 genus Rhadinichthys, and from their size and arrangement it is probable 



' Williams, H. U. Buffalo Soc. Nat. Sci. Bui. 1886. 5: 84, fig. 2. 



» Clarke, J. M. U. S. Geol. Sur, Bui. 16. 1&85. p. 20, 41, pi. i, fig. 2, 6. 



