8o Memoir Sears Foundation for Marine Research 



Hexanchus griseus (Bonnaterre), 1780 



Six-gilled Shark, Cow Shark, Grey Shark, Mud Shark 



Figures 8, 9 



Study Material. Female, 830 mm., from Nice, France (Harv. Mus. Comp. Zool., 

 No. 946); male, 429 mm., from off Havana, Cuba, apparently newborn, without trace 

 of umbilical scar (Harv. Mus. Comp. Zool., No. 35630) ; male, 4 feet, Puget Sound (U.S. 

 Nat. Mus., No. 104474); male, 1,167 mm-j from off Pacific Beach, California (Harv. 

 Mus. Comp. Zool., No. 36474) ; also jaws of an i i-foot and of a 5-foot specimen (Harv. 

 Mus. Comp. Zool., No. 36217, 36216) and of one of 10 feet 2 inches from N. Carolina 

 (U.S. Nat. Mus., No. 37790). 



Distinctive Characters. The presence of six gill openings, combined with the facts 

 that the lower ends of the members of each pair are widely separated one from the other 

 in the region of the throat, and that the upper teeth are strikingly unlike the lowers, 

 separates this species from all other sharks of the North Atlantic. 



Description. Proportional dimensions in per cent of total length. Male, 429 mm., 

 from Cuba (Harv. Mus. Comp. Zool., No. 35630). Female, 830 mm., from Nice, France 

 (Harv. Mus. Comp. Zool., No. 946). 



Trunk at origin of -pectoral: breadth 10.7, 9.8 ; height 8.2, 7.8. 



Snout length in front of: outer nostrils 1.6, 1.7; mouth 7.0, 5.0. 



Eye: horizontal diameter: 4.7, 3.0. 



Mouth: breadth 9.8, lO.O; height 6.3, 6.1. 



Nostrils: distance between inner ends 4.4, 4.6. 



Gill opening lengths: ist 6.S, 7-5; 2nd 5.4, 6.Ss 3rd 5.1, 5.8; 4th 4.7, 5.2; 5th 



3.4,4.3; 6th 3.5, 4.1. 



First dorsal fin: vertical height 3.7, 4.8 ; length of base 5.8, 6.6. 



Anal fin: vertical height 1.9, 3.5; length of base 4.4, 6.4. 



Caudal fin: upper margin 35.2, 31.3; lower anterior margin 10.2, 8.3. 



Pectoral fin: outer margin 13.O, 13.2; inner margin 5.2, 6.0; distal margin lO.O, 



10.7. 



Distance from snout to: ist dorsal 46.7, 54.1 ; upper caudal 64.8, 68.7; pectorals 



20.5, 21.3; pelvics 38.5, 44.6; anal 50.7, 57.2. 



Interspace between: ist dorsal and caudal 10.9, 9.0; anal and caudal 6.$, 5-2. 



Distance from origin to origin of: pectorals and pelvics 20.0, 25.4; pelvics and anal 



12.3,14.4. 



Trunk moderately stout anteriorly, its depth opposite origin of pectorals Vr to Vs as 

 great as its length to origin of caudal fin, tapering rearward and strongly compressed later- 

 ally posterior to pelvics. Caudal peduncle without precaudal pits. Lateral line clearly 

 visible as a pale streak from opposite last gill opening rearward out onto caudal and dip- 

 ping downward abruptly on anterior sector of caudal. Denticles on sides of trunk (Fig. 



