677 



Fig. 6. 



widely modified of the intercalated rays thus far known to occur 

 among the Cladoselachids has been described by Prof. Clatpole^) in 

 the pectoral of C. clarki: in this fin, Fig. 7, as many as three 

 radials have been in- 

 tercalated between the 

 tips of adjacent radials 

 in the most crowded 

 portion of the fin. 



The most inter- 

 esting of all types of 

 the pectoral fins of 

 Cladoselachids is now 

 for the first time shown, 

 Fig. 8. It occurs in 

 a species discovered by 

 Dr. Wm. Clark of 

 Berea, Ohio, whose 

 courtesy permits me to 

 refer to it, and it will 

 shortly be described by 

 Prof. Claypole. This 

 fin seems to present the 

 needed evidence that 

 among the Cladosela- 

 chids were forms which 

 had evolved spine- 

 shaped fins , closely 

 suggesting the hitherto 

 inexplicable fin struc- 

 tures of the Acantho- 

 dians. In the present 

 instance the fin is nar- 

 row, acutely pointed, 

 its proximo-distal width 

 nearly thrice as long as 

 its basal length: the 

 radials are stout, com- 



Fig. 7. 



Fig. 6. Pectoral of Cladoselache keplen. y(^ ^. 

 Fig. 7. Pectoral of C. clarki. X about |. 



1) American Geologist, Vol. XV, Jan. 1895. 



