SEXUAL CHARACTERS — ELASMOBRANCH FISHES 



231 



relationship is probably far apart. The apopyle, which is some 

 distance from the cloaca, leads into a deep pouch, which is con- 

 tinued posteriorly in a closed tube with soft edges, all as in 

 Cestracion (figs. 11 and 12). The small rhipidion in a similar 

 position is so reduced as to be negligible. The hamus is replaced 

 by a iQng, straight, thorn-like spur in a similar position. This 



Sk. 



Fig. 11 Pristiophorus cirratus. Sp., spur, enclosed in a sheath of skin 

 (Sk.); S., siphon. 



Fig. 12 Pristiophorus cirratus. A., apopyle; H., hypopyle; Sp., spur shown 

 erected in the upper sketch; S., siphon. 



spur can be erected as in figure 12 upper diagram, and is sugges- 

 tive of that of Acanthias save that it is perfectly straight, and 

 when at rest lies in a sheath of skin of its own. There is, how- 

 ever, no crumena. The clasper tube is more perfectly closed, 

 though still a scroll, and the hypopyle more distinctly defined. 

 The claspers are stout and have a flexure. 



The greatest difference between Cestracion and Pristiophorus 

 is that, whereas the former has a small siphon, in the latter it is 



JOURNAl. OF MOEPHOLOGT, VOL. 36, NO. 2 



