676 



Fig, 5. Pectoral fin of Cladoselache uewberryi. )^ about | 



will be seen to be by no means widely different from the ventral of 

 C. fyleri, Fig. 4: its apex is more pointed, its width is much greater 

 and the larger number of its radials, thirty-four, demonstrates that 

 when this element of the dermal fold was constricted otf it must have 

 been considerably longer than in the case of the ventral: its radials, 

 however, have the same characters as those of Fig. 4, differing little 

 in the regions of the fin, and showing the least tendency to inter- 

 calation: the intercalated rays, like the other radials, arise from the 

 body wall in the hinder part of the fin, but in the mid-region of the 

 fin they appear *) to taper away, terminating finally before the body 

 wall is reached. In its ancestral condition this fin seems unquestion- 

 ably to have been less acutely pointed, shorter in its distal direction, 

 and with its radials unintercalated : from the body wall outward it 

 may reasonably be represented in Fig. 1. Pectorals whose apices are 

 rounded are certainly known to occur: two of these are shown in 

 Figs. 3 and 6, C. fyleri and C. kepleri: these in some regards 

 may be regarded as more highly specialized than the pectoral of 

 Fig. 5: their radials are fewer in number, thirty-one, thirty-two, vary 

 widely in size and shape in different regions of the fin, and show 

 great unlikeness in the character of the intercalated rays. The most 



1) The writer is inclined to believe that ail of these intercalated 

 radials arise from the body wall on the other side of the fiu, the con- 

 centration of the radials causinf;^ their proximal ends to become wedge- 

 shaped in transverse section. Material is as yet lacking for the complete 

 demonstration of this view. 



