154 IOWA GEOLOGICAL SURVEY 



to have been absolutely straight from base to summit. Along 

 the line of junction between the enameled and buried portions 

 the spine must have been 2 inches wide, but it tapered rapidly 

 upward, terminating in a slender, acute point. The exposed 

 surface is more completely covered with ridges similar in char- 

 acter, and the pectination is more crowded than in any other 

 species known to me. In its broad base and its general and 

 uniform ornamentation this spine has some resemblance to 

 C. speciosus St. J. & W., specimens of which have been in my 

 hands, but the line of demarcation between the ornamented and 

 buried portions is less oblique, showing that the spine was more 

 erect [and hence referable to the anterior dorsal fin] ; the ridges 

 are considerably coarser and the form is straighter. The pectin- 

 ation is also less oblique and close, compared with the coarse- 

 ness of the ridges. 



Formation and locality. Moscow shale (Hamilton division of 

 the Erian) ; Kashong creek, Yates county, New York. 



Gtenacanthus randalli Newberry. 



1889. Ctenacanthus randalli J. S. Newberry, Monogr. U. S. Geol. Surv. 16, 



p. 105. 

 1907. Ctenacanthus randalli C. E. Eastman, Mem. N. Y. State Mus. 10, p. 77. 



This species, which has never been illustrated, is founded 

 upon the proximal portion of an extremely large spine, esti- 

 mated to have been at least 30 cm in length. The original de- 

 scription is here reproduced as follows : 



Dorsal fin spines 12 inches or more in length by 1% inches 

 in width at base of ornamented portion; form slightly curved 

 backward, sides compressed, basal portion conical, smooth or 

 finely striated longitudinally; line of demarcation between orna- 

 mented surface and base strongly marked, inclined downward 

 and forward at an angle of 30° with the axis of the spine; orna- 

 mented surface near base formed by about 40 parallel, subequal, 

 closely crowded ridges on each side of the median line, and these 

 bear small rounded closely approximated tubercles. 



Formation and locality. Olean conglomerate (Chemung 

 group) ; near Warren, Pennsylvania. 



Ctenacanthus chemungensis Claypole. 



1885. Ctenacanthus chemungensis E. W. Claypole, Proc. Amer. Assoc. Adv. 



Sci. 33d meeting, p. 490 (name only). 

 1907. Ctenacanthus chemungensis C. R. Eastman, Mem., N. Y. State Mus. 10 , 



p. 77, pi. 7, fig. 3. 



