134 Memoir Sears Foundation for Marine Research 



Sex Characters. On the dorsal side of the outer part of each pectoral, adult males 

 have from one to five rows of claw-like "alar" spines, retractile in grooves of the skin. 

 It is supposed that they play some role in holding the female during copulation, but 

 just how is not known. Also, in some species, either in female alone or in both sexes 

 when mature, there may be a belt of large, nonretractile, so-called "malar" thorns on 

 the outer anterior parts of the disc, between the anterior ends of the pectoral rays and 

 the level of the spiracles. Furthermore, large thorns or bucklers are usually much 



Figure 27. A Pelvis oi Raja ocellata, female, about 790 mm long, from Waquoit, Massachusetts (Harv. Mus. 

 Comp. ZooL, No. 359); dorsal view on right; about 0.5 x. B Gill arch (above) and lateral view of gill fold 

 (below) of Raja laevis, from off Nantucket Island (Harv. Mus. Comp. ZooL, No. 36691), about 0.8 X. 



more highly developed or more numerous in adult females than in adult males; the 

 latter are the smoother in general. The degree to which the anterior margins of the 

 disc are concave in outline also differs in the two sexes in some species. 



Development is oviparous in all rajids in which it is known and doubtless in all 

 other members of the family as well. The egg cases are quadrate with thick horny 

 shells, their corners prolonged as long flexible horns (see also p. 141). 



The claspers' are cylindrical, narrowing gradually from base toward tip in early 

 stages of growth but becoming more or less dilated terminally with the approach of 

 sexual maturity, at which time they extend considerably beyond the tips of the pelvic 

 fins. The seminal groove along the outer face of the clasper is wide open for a con- 



5. For recent accounts of the claspers in various European Skates, see Jungersen (Danish Ingolf Exped., 2 [2], 1898: 

 56, pi. 4, figs. 45-57; pi. 6, figs. 67, 68), Huber (Zool. Anz., 32, 1901: 717), and Leigh-Sharpe (J. Morph., 34, 

 1920: 260; 36, 1922: 236, 242, fig. 19), who shows the claspers of Kaja blanda when relaxed and distended; he also 

 gives brief descriptions of various other European species (J. Morph., J9, 1924: 567-577)- 



