366 



W. HAROLD LEIGH-SHARPE 



as in Scyllium. There are therefore a distinct apopyle and 

 hypopyle. The rhipidion is well developed. The distal end of 

 the clasper is jointed, so that, by the aid of muscular contrac- 

 tion, the terminal portion of the clasper can be flexed abruptly 

 outward, thus affording a powerful means of attachment during 

 copulation, analogous with the spur already described in Acan- 

 thias. A hint of such an outward flexure can be seen occasion- 



Fig. 5 Mustelus vulgaris 

 pseudosiphon ; Pe., pera. 



14 



12 



lO 



H., hypopyle; Rh., rhipidion; Ps., 



ally in Scyllium canicula, although I am much in doubt whether 

 such a modification is characteristic of Scyllium, since about 8 

 per cent of the individuals that come under my notice have the 

 distal ends more markedly developed toward a spoon-shaped 

 conformation, and these alone seem capable of such a flexure. 

 Toward the posterior end of the clasper, at about the middle 

 length of the rhipidion, upon its inner border, but coming to lie 

 upon its outer border owing to natural torsion, is a small blindly 

 ending sac, the pseudosiphon, whose aperture points in a pos- 



