16 THE PLAGIOSTOMIA. 



Hexanchus. 



Hexanchus Rafinesque, 1810, Caratteri, p. 14. 



Six gill openings; margin of first gill cover not free across the isthmus. 

 Mouth wide, shorter than the skull, with a rudimentary labial fold on the lower 

 jaw at the angles. Teeth dissimilar, anterior of upper jaw raptorial, lower teeth 

 sectorial, compressed in cusps and bases. Eyes lateral. Spiracles minute. 

 Fins moderate, a notch near the tip of the caudal. 



Mediterranean; Atlantic; Eastern Pacific. 

 Median tooth of lower jaw with or without a medial cusp 



seven cusps, or more on lateral teeth of lower jaw 



inner edge of primary cusp without serrations griseus (page 16) 



Median tooth of lower jaw with a small medial cusp 



six cusps on lateral teeth of lower jaw 



inner edge of primary cusp with fine serrations corinus (page 17) 



Hexanchus griseus. 



Vacca Scilla, 1759, De corp. mar. lap., pi. 1, 27, 28. 



Le griset Brotjssonet, 1780, Mem. Acad, roy., p. 663. 



Squalus griseus Bonnaterre, 17S8, Ichth., p. 9; Gmelin, 1789, Linn6 Syst., 1, p. 1495; Schneider, 



1801, Bloch Ichth., p. 129; Risso, 1810, Ichth. Nice, p. 37. 

 Le squale griset Lacepede, 1798, Poissons, 1, p. 269. 

 Squalus vacca Schn., 1801, Bloch Ichth., p. 138. 

 Hexanchus jriseus Rafinesque, 1810, Caratteri, p. 14; 1810, Ind. itt. Sic, p. 47; Muller& Henle, 1841, 



Plagios., p. 80; Yarrell, 1836, Brit, fishes, 2, p. 515; Dumeril, 1865, Elasm., p. 431, pi. 4, fig. 



9-12; Moreau, 1881, Poiss. France, 1, p. 339; Jord. & Everm., 1896, Bull. 47, U. S. nat. mus., 



p. 19; 1900, ibid., Atlas, pi. 2, fig. 8; Regan, 1905, Ann. mag. nat. hist., ser. 7, 16, p. 571 (part). 

 M onopterinus griseus Blainv., 1816, Bull. Soc. philom., p. 121; 1830, Poiss. Fr., p. 77. 

 Notidanus griseus Cuvier, 1817, Reg. anim., 2, p. 128; Agass., 1835, Rech. poiss. foss., pi. E, fig. 2-4; 



1838, ibid., Texte, p. 92; 1843, ibid., 3, p. 216; Bonaparte, 1841, Icon. Fauna Ital., Pesci, fig.-; 



Couch, 1846, Zool., p. 1337; 1865, Brit, fishes, 1, p. 21, pi. 4; Bocage & Capello, 1866, Plagios., 



p. 15; Gunth., 1870, Cat. fishes Brit, mus., 8, p. 397. 

 Notidanus vacca Cuv., 1817, Reg. anim., 2, p. 128. 

 Notidanus monge Risso, 1826, Hist, nat., 3, Poissons, p. 129. 



Body moderately elongate, cavity little more than half, head near one fifth, 

 and tail one third, or more, of the total length. Head large, broad, depressed; 

 snout short, blunt. Nostrils small, near the end of the snout. Eye as long as 

 the snout. Spiracle small, far behind the eye. Six wide gill openings in front 

 of the pectoral. Mouth large, a groove behind its angle reaching half way to the 

 gill aperture, with a labial fold mainly on the lower jaw at the angle. No 

 median tooth on the upper jaws; anterior teeth slender, sharp, without or with 

 basal cusps; anterior two or three of lateral teeth larger with a single cusp at 

 the outer side of the primary, posterior lateral teeth with two or more outer 



