220 



W. HAROLD LEIGH-SHARPE 



Rhinobatus appears to be a more primitive skate-like form for 

 the following reasons: 1) The claspers are denticled all over. 

 2) The rhipidion is not well developed, and is not in the form of 

 a fan. 3) The clasper gland is very small in comparison with the 

 size of the animal. 4) A similar fossil species dates back to 

 cretaceous times. 



On the other hand, it is specialized in the following points: 

 1) The web expansion over the sentina with, 2) a claw. 



s.s. 



c.i. 





3 mm 



la 



Fig. 22 Rhinobatus productus, a transverse section of the clasper gland, 

 (haemalum-eosin). CI., one component of the gland; C2, another component; 

 PI., papilla of the first component; P2, papilla of the other component; M., 

 stripe muscle; S. S., siphon sac. 



