DEVONIAN FISHES OF IOWA 155 



This name was applied by Professor Claypole without defini- 

 tion or illustration to small fin-spines obtained by him from 

 the Chemung of Bradford county, Pennsylvania, whose length 

 was stated to be "less than half that of Ct. vetustus". 



To this species are probably to be' referred a number of small, 

 gently arcuate, finely ornamented spines which were collected 

 by the late Professor Charles E. Beecher and others from the 

 Chemung of Warren county, Pennsylvania, examples of which 

 are preserved in the Yale and Harvard Museums. Spines of 

 the same general character have also been obtained from two or 

 three localities in New York State, as for instance between 

 Friendship and Nile, and along the bank of Fall creek near 

 Ithaca, at different levels in the Chemung Group. 



None of these spines appear to have exceeded 10 cm in total 

 length and they are frequently much shorter, their form being 

 narrow and gradually tapering. The flattened sides are cov- 

 ered with numerous filiform costae, as many as twenty being 

 observed toward the base, and these are for the most part con- 

 tinous; when new longitudinal costae are formed their origin 

 is by implantation. The costae are finely pectinated at intervals 

 varying from twice to three times their own width, thus giving 

 rise to a finely punctuate appearance when seen in impression as 

 is usually the case. 



Formation and locality. Chemung group; New York and 

 Pennsylvania. 



Post-Devonian Species of Ctenacanthus. 



More than a dozen species of this genus have been founded 

 upon detached fin-spines occurring in the Kinderhook lime- 

 stone near Burlington, LeGrand, and other localities in Iowa, 

 but without exception their relations seem to be rather with 

 Carboniferous sharks (Cochliodonts!) than with Devonian 

 Pleuropterygii. An interesting correlation has been established 

 between two distinct series of fin-spines and their probable posi- 

 tion in advance of the anterior and posterior dorsal fins, as 

 already noted. In the following list, the series formed by C. 

 varians, spectabilis, deflexus, solidus, clarki and brevis, all char- 



