SEXUAL CHARACTERS — ELASMOBRANCH FISHES 



223 



females, unless the fins are parted, and, in the large specimen, 

 the fins may be mistaken for the claspers. The claspers are 

 obviously in a very primitive condition, and look hke a dupUca- 

 tion of the fins, resembling a rolled-up leaf, so that the closed 



Fig. 2 Notidanus griseus. Sh., sheath formed by pelvic fin; CI., clasper; 

 A., apopyle; H., hypopyle; S. Ap., aperture of 'siphon' tube; Ex., position of the 

 external sheath sac indicated in dotted outline; Su., sulci; a -a', b-b', cartilages 

 cut through in dissection. 



tubular portion is brief. They are not covered with denticles, 

 and have little or no skeletal support. 



Between the outer border of each clasper and its sheathing 

 fin is an external sac which is not merely a groove formed in the 

 union of clasper and fin, but a space of considerable length (fig.l). 

 In figure 2 the position of this sac is indicated in dotted outline. 



