180 BULLETIN 10 0, UNITED STATES NATIONAL MUSEiUM 



in snout, 24^ to 3 in interorbital ; mouth gape % its width to % 

 latter, 3i/^ to 3% in head; preoral length 2 to 2% in head; teeth 

 large, serrate, upper broadly triangular with slightly curved ends 

 and lower narrower teeth more erect; nostril moderate, with very 

 obtuse flap, little nearer mouth than snout tip or midway ; internasal 

 % to % of mandible width; interorbital 2 toi 21/5 in head, broad, 

 depressed, very slightly convex. Gill openings about long as eye, 

 last 2 above pectoral base. 



Scales minute, each with 3 keels. 



First dorsal about midway between snout tip and subcaudal origin 

 or midway between paired fins, front edge 1% to 2% in head; second 

 dorsal length 2% to 3 ; anal similar, little smaller and opposite second 

 dorsal, length 3 to 3% ; caudal 2% to 2% in rest of body, subcaudal 

 2% to 3 in caudal length; pectoral 3 to 4% in combined head and 

 body to subcaudal origin, width 2% its length; ventral inserted 

 nearly midway between origins of dorsals, length 2% to 3 in head. 



Gray to light blue, sometimes with violaceous tint in young, on 

 upper surfaces. Sometimes adults neutral slaty or gray black. 

 Lower surfaces of body white, often soiled. 



South Africa, China, Japan, Lord Howe Island, Queensland, New 

 South Wales, Tasmania, New Zealand. Also in the Eastern Pacific 

 and throughout the Atlantic. 



The blue shark is so called from its color, which is always a deep 

 blue on the upper half of the body, the under surface white. In the 

 young the blue color is often very brilliant and with violet or purple 

 tints. Its food is cliiefly fish. 



" When in pursuit of prey or excited, they continually cover and 

 uncover their eyes with their nictitating membrane. The time of 

 their greatest activity is at night, when they may be seen stealing 

 through our summer seas like beasts of prey: their bodies not even 

 disturbing the phosphorescence which at that time of the year so 

 fills the ocean. A most puzzling circumstance ; and but for the flex- 

 ible part of the dorsal fin and tip of the tail, it would be impossible 

 to detect their presence in the darkest night." (Dunn.) 



U.S.N.M. Nos. 52637-52640. Lat. 28°31'00" N., long. 141°47'0O" W. (Hawaii). 

 Bureau of Fisheries, 1901-1902. 



U.S.N.M. Nos. 52645-52650. Lat. 28°31'0O" N., long. 141°47'00" W. Bureau of 

 Fisheries, 1901-1902. 



U.S.N.M. No. 52676. Hawaii. Bureau of Fisheries, 1901-1902. 



U.S.N.M. Nos. 52765, 52766. Honolulu. Bureau of Fisheries, 1901-1902, 



U.S.N.M. No. 54605. Lat. 28°31'00" N., long. 141°47'00" W. Bureau of Fish- 

 eries, 1902. 



U.S.N.M. No. 55001. Lat. 28''31'00" N., long. 141°47'00" W. Bureau of Fish- 

 eries, 1901-1902. 



U.S.N.M. No. 58538. Lat 28°31'00" N., long. 141°47'00" W. Bureau of Fish- 

 eries, 1901-1902. 



