18 THE PLAGIOSTOMIA. 



Dorsal small, little higher than the anal, above the middle of which it termi- 

 nates. Ventrals small extending behind the origin of the dorsal. Tail long, 

 twice as long as the head, little less than one third of the total, scales on the upper 

 edge of the caudal fin somewhat enlarged. 



Uniform dark brown to black, greyish below. Young specimens brown. 



Type described, forty-three inches long, from Neah Bay; young from 

 Soquel, Bay of Monterey. 



NOTORYNCHUS. 

 Notorynchus Ayres, 1855, Proc. Cal. acad. sci., 1, p. 73; 1873, p. 77 (reprint). 



Resembling Hexanchus, but with seven gill openings. Head broad, de- 

 pressed, snout broad. Mouth wide, broadly curved in front, with a labial fold 

 from the angle on the lower jaw, and with a deep groove behind the angle. 

 Teeth dissimilar, anterior of the upper raptorial; lower teeth sectorial, com- 

 pressed in cusps and bases, 6 broad laterals on a lower jaw. Nostrils anterior. 

 Eyes lateral. Spiracle small. Dorsal small, behind the ventrals. Pterygo- 

 quadrate loosely articulated to the posterior and lower side of the postorbital 

 process; hyomandibular stout. 



Species, N. primigenius and N. serraiissimus, apparently of this genus were 

 described by Agassiz from the Eocene of England. 



No median tooth in the upper series 



a median cusp on median lower tooth present or absent 



primary cusp of lower lateral teeth little the larger, denticles of inner 

 edge weak or absent ..... platycephalus (page 18) 



A median tooth in the upper series 



no median cusp on the median lower tooth 



primary cusp of lateral lower teeth little larger, denticulate on the 

 inner edge pectorosus (page 20) 



Notorynchus platycephalus. 



Squalus platycephalus Tenore, 1809, Mem. Acad. Pont., 1, p. 241, 258. 



Notidanus sp. Cuvier, 1829, Reg. anim., 2, p. 390. 



Notidanus indicus Agassiz, 1835, Rech. poLss. foss., pi. E, f. 1, Feuilleton, p. 71; 1838, ibid., Texte, 



p. 92; 1843, ibid., p. 217; GtJNTH., 1870, Cat. fishes Brit, mus., 8, p. 378 (part). 

 Heptanchus indicus Muller & Henle, 1841, Plagios., p. 82, pi. 32 (teeth); Schlegel, 1850, Jap. Pisces, 



p. 303; DuM^RiL, 1865, Elasm., p. 434. 

 Heptanchus platycephalus Costa, 1854, Chondr., Squal., p. 12, pi. 14, f. 1, 2, 4-6. 

 Notorynchus maculatus Ayres, 1855, Proc. Cal. acad. sci., 1, p. 72; 1873, p. 76 (reprint). 

 Heptanchus maculatus Girard, 1858, Rept. Pacif. R. R., Fish, p. 367. 



