5IO 



Memoir Sears Foundation for Marine Research 



males, 465 and 501 mm. long, from Japan (Harv. Mus. Comp. ZooL, No. 1368, 1245); 

 female about 485 mm. long, from the vicinity of Albemarle Island, Galapagos, Lat. 2° 

 34' N., Long. 92° 06' W., in a trawl haul from 1,360 fathoms. Albatross Sta. 3413 

 (Harv. Mus. Comp. Zool., No. 1005). 



Distinctive Characters. Isistius is separated from all other northwestern Atlantic 

 sharks of its suborder except Dalatias by the triangular shape of its lower teeth j the posi- 



FiGURE 99. Isistius brasiliensis, pictured in Fig. 98. Upper and lower teeth, left-hand side, about 4.4 x. 



tion of its first dorsal fin far rearward marks it off at a glance from Dalatias. It shares this 

 last character with Echinorhinus, but there is no danger of confusing it even with new- 

 born specimens of the latter, for the shape of its caudal, its teeth and its dermal denticles 

 are very different and its gill openings much smaller. 



Description. Proportional dimensions in per cent of total length. Male, 383 mm., 

 from Lat. 25° 1 1' N., Long. 77° 19' W. (Harv. Mus. Comp. ZooL, No. 36039). Female, 

 501 mm., from Tokyo, Japan (Harv. Mus. Comp. Zool., No. 1245). 



Trunk at origin of -pectoral: breadth 10.2, ii.O; height 8.4, ii.o. 



Snout length in front of: outer nostrils 0.8, 0.8; mouth 7.0, 6.6. 



Eye: horizontal diameter 3.4, 3.2. 



Mouth: breadth 4.7, 4.2; height O, o. 



Nostrils: distance between inner ends 1.6, 1.4. 



Labial furrow length from angle of jaw: upper 4.2, S-^- 



Gill opening lengths: ist 0.8, 0.8; 2nd 0.8, 0.8; 3rd 0.8, 0.8; 4th 0.8, 0.8; 5th 



0.8,0.8. 



First dorsal fin: vertical height 3.4, 2.6; length of base 3.1, 3.2. 



Second dorsal fin: vertical height 2.9, 2.4; length of base 3.9, 3.8. 



Caudal fin: upper margin 14.6, 15.3; lower anterior margin 1 1.2, 10.2. 



Pectoral fin: outer margin 7.8, 7.3; inner margin 4.4, S-6; distal margin 4.2, 4.2. 



Distance from snout to: ist dorsal 59.5, 59-3; 2nd dorsal 70.5, 71.8; upper caudal 



85.4, 84.7; pectoral 19. i, 17.9; pelvics 60.1, 62.8. 



