Fishes of the Western North Atlantic 



411 



in that the anterior contour of the head is unmistakably indented in the midline. But it 

 differs from tudes in the much more definitely marked prenarial groove, more erect first 

 dorsal, and less deeply concave second dorsal, as well as in the fact that the teeth are 

 smooth-edged (serrate in tudes) with the lowers noticeably more slender and more erect 

 than the uppers. The most obvious diflFerences from diplana are: eyes relatively much 

 smaller, the free rear tip of the second dorsal not longer than the anterior margin of 

 latter (twice that long in diplana), origin of pelvics almost under rear tip of first dorsal 

 (considerably behind it in diplana) and the anal less deeply concave and considerably 

 longer than the second dorsal. It is separated from zygaena by: the relatively long, 

 narrow hammer which is scalloped anteriorly in the midline, the very short free rear 

 corner of the second dorsal, the lower teeth which are much more slender and oblique than 

 the uppers, and the anal fin which is much longer than the second dorsal. The shape of the 

 head separates it from tiburo. 



Figure 80. Sphyrna bigelouii, illustrated in Fig. 79. Head from below, about 0.6 X. 



