64 NEW YORK STATE MUSEUM 



representatives in the American Paleozoic. The Acanthodidae range from 

 the Lower Devonic to the Lower Permian inclusive, the Diplacanthidae 

 are confined to the Upper Siluric and Lower Devonic. The detached fin 

 spines known as Machaeracanthus, Gyracanthus, and similar forms are 

 regarded with much probability as belonging to fishes of this order. 



Acanthodes ? pristis Clarke 



1885 Acanthodes ? pristis J. M. Clarke. U. S. Geol. Sur. Bui. 16, p. 42 

 1891 Acanthodes ? pristis A. S. IVoodzvard. Cat. Foss. Fishes Brit. Mus. pt 2, 



P- 15 

 1902 Ac an t h o e s s u s ? pristis 0. P. Hay. U. S. Geol. Sur. Bui. 179, p. 273 



Founded upon a considerable portion of the shagreen of an undoubted 

 Acanthodian fish, the family position of which, owing to the nonpreserva- 

 tion of fins, is uncertain. In the solitary specimen known, the greater 

 number of scales have retained their natural, exceedingly compact arrange- 

 ment, and are so minute as to indicate a species of very diminutive size. 

 Their characters are given in the original description as follows . " The 

 scales are very small, measuring .5 mm on the edge, square or slightly sub- 

 rhomboidal in outline, and one fourth as thick as wide. The adjacent 

 edges at about two thirds the distance from the upper surface are strongly 

 grooved by a single deep furrow. The upper surface of the scales is 

 smooth and slightly convex." 



The type specimen, which belongs to the United States National 

 Museum, was obtained by Dr J. M. Clarke from the bituminous layers of 

 the Portage beds (Rhinestreet shale) exposed in a Delaware and Lacka- 

 wanna railroad cutting near the town of Sparta, N. Y. In Woodward's 

 and Hay's catalogues, cited in the above list of references, the species is 

 erroneously reported as from the Genesee shales of New York in which 

 Palaeoniscid scales of the same character are known to occur. 



Order SELACHII 

 To this order, which includes the sharks and skates, numerous Paleo- 

 zoic teeth and fin spines have been ascribed, but only on account of their 

 close resemblance to the corresponding hard parts of recent forms. So far 



