HEXEPTRANCHIDAE. 15 



openings six, very wide, oblique, in front of the pectorals; those of the two sides 

 narrowly separated on the isthmus, which is crossed by the free margins of the 

 first gill cover. 



Pectorals moderate, broad, rounded. Dorsal small, base opposite and 

 shorter than that of anal. Anal larger than ventrals, tip reaching origin of 

 caudal. Caudal long, pointed, armed on upper edge by modified scales, sub- 

 caudal deep anteriorly, narrowing backward, not separated by a notch from 

 the tip. 



Uniform brown. 



Details of anatomy are given by Garman, 1885, with numerous figures, and 

 by Gunther, 1887. 



The type was taken in Japan, where the species is hardly to be considered 

 rare. Collett, 1890, reports the occurrence of the species at Funchal, Madeiras, 

 and, 1897, from Varanger Fjord, Norway. Females with eggs were taken by 

 Mr. Alan Owston from depths of 360 fathoms in the Sagami Sea, Japan. 



Hexeptranchidae. 



Body elongate, head depressed, caudal long. Eyes lateral, without a nicti- 

 tating membrane. Nostrils near the end of the snout, not connected with the 

 mouth. Mouth large, inferior, with a labial fold on the lower jaw at the angle. 

 Teeth more or less comb-like, compressed, with slender bases and varying num- 

 bers of pointed cusps. Spiracles present, small. One dorsal, not preceded by 

 a spine, behind the ventrals. An anal fin. Gill openings six to seven, in front 

 of the pectorals, margins of covers not free across the isthmus. A spiral valve 

 in the intestine. Many species of several genera are known from the Creta- 

 ceous and the Tertiary. 



Six gill apertures 



pterygoquadrate loosely articulated behind the postorbital process; hyo- 

 mandibular moderate, elongate 



head broad; snout broad Hexanchus (page 16) 



Seven gill apertures 



pterygoquadrate loosely articulated to postorbital process; hyomandibular 

 stout 

 head broad; snout broad .... Notorhynchus (page 18) 

 pterygoquadrate firmly articulated to the postorbital process; hyomandi- 

 bular slender 

 head tapering; snout narrow . . . Heptranchias (page 21) 



