124 Memoir Sears Foundation for Marine Research 



identical 5 also, if the original account be correct, a third Indian Ocean species {guntheri 

 Murray, 1884) that differs from glaucus in having about twice as many teeth and a much 

 more prominent lateral line.°° 



Key to Species 



I a. Teeth about 12-14 on each side on each jaw; lateral line not forming a prominent 



ridge along the side. 



2a. Height of ist dorsal about one-half as great as distance from eye to 4th gill open- 

 ing and a little greater than length of its base ; length of head to origin of pectoral 

 about as great as from axil of pectoral to rear ends of bases of pelvics (or distance 

 from axil of pectoral to origin of pelvics only about as long as from tip of snout 

 to 2nd gill opening) . oxyrinchus Rafinesque, 1 8 1 o, p. 124. 



2b. Height of ist dorsal only about one-half as great as distance from eye to 2nd gill 

 opening and a little less than length of its base; length of head to origin of pec- 

 toral only about as great as distance from axil of pectoral to origin of pelvics (or 

 distance from axil of pectoral to origin of pelvics about as long as from tip of 

 snout to origin of pectorals). glaucus Miiller and Henle, 1841.'° 



Indo-Pacific. 

 lb. Teeth 22-28 on a side in each jaw; lateral line forming a prominent ridge along the 

 side, rearward to caudal peduncle. guntheri Murray, 1884. 



India." 



Isurus oxyrinchus Rafinesque, 1810 



Sharp-nosed Mackerel Shark, Mako 



Figures 18, 19 



Study Material. Skin, with head attached, of adult male, 7 feet 6 inches long, from 

 Bimini, Bahamas (Harv. Mus. Comp. Zool., No. 35367); young male (entire), 1,640 

 mm., from Ocean City, Maryland (Harv. Mus. Comp. Zool., No. 35899); skin, about 

 6 feet long, from Miami, Florida (Harv. Mus. Comp. Zool., No. ZSZ^^)'-! ^^so female 

 (mounted) from Miami, Florida, about 6 feet 8 inches long; jaws from medium-sized 

 and large specimens taken off New Jersey, New York and Cape Cod (U.S. Nat. Mus., No. 

 iio88i, Amer. Mus. Nat. Hist., No. 567 and 9220, Harv. Mus. Comp. Zool., No. 816). 



Distinctive Characters. The Mako is separable from the common Mackerel Shark 

 by its teeth and more slender form; from Carcharodon by its teeth, its slender form and by 

 the relative position of the second dorsal and anal fins. 



29. Only one specimen of this sort has ever been reported (Murray, Ann. Mag. nat. Hist., [5] 13, 1884: 349). 



30. Including bideni PhiUipps (N. Z. J. Sci. Tech., 13, 1932: 227, fig. 2, S. Africa); mako Whitley (Rec. Aust. 

 Mus., ly, 1929: loi). 



31. Only one specimen of this sort has ever been reported (Murray, Ann. Mag. nat. Hist., [5] ij, 1884: 349) ; the 

 validity of this species is very doubtful. 



