24 CRETACEOUS AND TERTIARY FISH. 



laterally, besides small posterior. Gill slits 6 or 7. Spiracle 

 small. Dorsal 1, no spine, opposite and like anal. No caudal 

 pit. Viviparous. 



Living species in warm seas, some reaching a very large size. 

 Genera 2 or 3. 



Genus HEPTRANCHIAS Rafinesque. 



Heptranchias Rafinesque, Car. Nuov. An. Sicil., 1810, p. 13. Type Squalus 



cinereus Gmelin, monotypic. 

 Heptanchus, Heptancus, auct. 

 Aellopos Agassiz, Poiss. Foss., Ill, 1843, p. 376. Type Aellopos wagneri 



Agassiz, first species. 

 Notorynchus Ayres, Proc. Cal. Acad. Sci., I, 1856, p. 72. Type Notoryn- 



chus maculatus Ayres, monotypic. 

 Notorhynchus, auct. 



Differs from Hexanchus in the presence of seven gill-openings. 

 The fossils referred to this genus are only known from detached 

 teeth. About 11 living, and about 33 extinct species have been de- 

 scribed, mostly under the generic name Notidamis, which is 

 properly a synonym of the earlier Hexanchus. 



Heptranchias primigenius (Agassiz). 



Notidamis primigenius Cope. Proc. Amer. Philos. Soc. Phila., XIV, 1875, 

 p. 362 (Cumberland Co., Miocene). 



Lateral teeth wide, thin, and greatly compressed. Coronal 

 region wide, polycuspid, faces similarly convex, smooth and 

 compressed. Cutting-edges entire. Anterior cusp enlarged, well 

 inclined externally, and followed by 6 or 7 similar ones gradu- 

 ated to last, latter quite small. Preceding largest cusp 6 to 10 

 anterior small graduated cusps, graduated down, first scarcely 

 larger than penultimate or last of external cusps. Graduation 

 of these cusps also slight, as all small. Apices of all cusps com- 

 pressed, not twisted. Root compressed, rather thin, outer face 

 flattened and inner bulging a little convexly. Lower margin 

 entire or slightly convex. In transverse section root somewhat 

 cuneate. Height of largest example 20 mm. 



