10 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



above, 10 below; upper teeth each with slender curved hooked cusp, 

 in front simple and some outer or hind ones, of latter 1 or 2 minute; 

 lower teeth each with 6 or more cusps, very small notch in front, 

 second cusp enlarged, others following small; nostrils small, lateral 

 on side of snout, nearly midway in space between snout tip and front 

 of mouth ; interorbital 3% to 3% in head, moderately broad, little de- 

 pressed. Gill openings equidistant, graduated smaller from first 

 which largest and extends forward last third in head, last before 

 pectoral base. 



Scales minute, median point much longest, 3 keels with median 

 longest and strongest. 



Dorsal origin opposite depressed ventral tips, front edge 2% to 2% 

 in head, hind lobe ends in narrow short point; anal origin opposite 

 middle of dorsal base or little posterior, front edge 3% to 4l^ ; caudal 

 2 to 2% in rest of body, subcaudal front edge 2 to 2l^ in head ; least 

 depth of caudal peduncle 4; pectoral 1% to 1%, width ll^ to I14 its 

 length ; ventral 2. 



Dull gray brown above, paler to whitish below. Fins dull brown- 

 ish. Iris pale yellowish brown. 



Japan, New South Wales, Victoria. In the eastern Pacific at Chile 

 and also in the Atlantic and Mediterranean. 



A.N.S.P. nos. 542, 543, Italy. C. L. Bonaparte (no. 245). Length, 815 to 840 



mm. 

 2 examples, A.N.S.P. No data. Two dried skins. 



Genus HEXANCHUS Rafinesque 



Hexanchus Eafinesqtje, Caratteri animali piante Sicilia, p. 14, 1810. (Type, 



Squalus griseus Bonnaterre, monotypic. ) 

 Hexancus Agassiz, Nomencl. Zool., Index, p. 181, 1846. (Type, Squalus griseus 



Bonnaterre.) 

 Monopterlimus Biainville, Bull. Soc. Philom. Paris, 1816, p. 121. (Tsrpe, 



Squalus griseus Bonnaterre.) 

 Notidanus Cuvier, Regne animal, vol. 2, p. 128, 1817. (Type, Squalus griseus 



Bonnaterre, designated by Jordan and Evermann, Genera of fishes, pt. 1, 



p. 97, 1917.) 

 Notidanms Mijnsteb, Beitr. Petrefak., vol. 5, p. 66, 1842. — Desmakest, in Chenu's 



Encyclop. Hist. Nat., vol. 19, p. 349, 1874. (Type, Sqtialus griseus 



Bonnaterre. ) 



Body partly cylindrical, cavity little over half total. Eyes lat- 

 eral. Mouth width shorter than skull, crescentic, with rudimentary 

 labial fold on lower jaw at angle. Teeth dissimilar, anterior upper 

 raptorial, lower teeth sectorial and compressed in cusps and bases. 

 Gill openings 6, edge of first gill cover not free across isthmus. 

 Spiracle small, on side of neck. Dorsal single, spineless, nearly 

 opposite anal. Caudal axis low and no caudal pit, subcaudal present. 



Tropical and subtropical seas. 



