SEXUAL CHARACTERS — ELASMOBRANCH FISHES 



237 



batus (Memoir IV, p. 218), while its inner border is raised into a 

 prolonged spike having a strong cartilaginous support to prop 

 the oviduct open. The rhipidion is elongated and not in the 



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cin 



Fig. 16 Raia clavata. CI. GL, clasper gland; A., apopyle; H. hypopyle; 

 Rh., rhipidion; Sg., signal; Sn., sentinel; Ps., pseud osiphon; Sp.. spike; St., 

 sentina, 



form of a fan; owing to its being twisted out of one plane, its 

 function is very effectively performed. Posterior to the hypo- 

 pyle, at the level of the commencement of the rhipidion, is a 

 soft, fleshy pad, the signal, resembling the 'foot' of a bivalve 

 mollusc, which, during erection, turns laterally through an 



