Jordan and Rvcr/nann. — Fishes of Nortli America. 19 



19. HEXANCHUS GRISEUS, (Liim'liii). 

 (Cow Suauk;Cana-I5ota.) 



Head large, depressed, blunt, the nostrils near tip of snout; no median 

 upper tooth ; 2 on each side entire, hooked outward ; the next teeth 

 with 6 or 7 cusps, the others similar; lower median tooth small, without 

 cusp: lateral teeth each with 7 to 9 cusps, the number of denticles on 

 most of the teeth being thus greater than in IT. corhius. Tail not twice 

 head, 3i in length, its upper scales enlarged; pectoral shorter than 

 lower jaw from gill opening. Color dark gray. (Day), L. 8 to 2(5 feet. A 

 very large shark inhabiting deep water, in the Mediterranean, thence 

 north to the west coasts of Scotland ; also frequently taken in Cuba. 

 (Poc)/). (yvMciis, gray.) (Eu.) 



Squfdus grisens, Gjielin, Sj'st. Nat., 1405, 1788, Mediterranean, after Broussouct. 



/Sf/H(t?Ms griseus, Bonnaterre, Tabl. Encycl. Ichtli., 9, 1788, Mediterranean, afteT Giiset of 



BrouBsonot. 

 Notidarms grisens, GiiNTUER, Cat., Vlll, 397, 1870. 

 Notidauus griseus. Day, British Fishos, 308, 1870. 

 Hexanchus griseus, PoEV, Synopsis, 454, 1875. 



Order E. ASTEROSPONDYLI. 

 (The Typical Sharks.) 



The essential character of this order is in the structure of the vertebne. 

 The calcareous lamelhe within each vertebra radiate from the central 

 ring. The group contains the great body of living sharks, including all 

 of those with 5 gill openings, 2 dorsals, and an anal iin. {uan/p, star; 

 aTr6i>dv?i.ur, vertebra.) 



SUBOKDEKS OP AsTEROSrONDYLI. 



a. PalatuquaJrate apparatus articulated to preorbital part of skull; dorsal fins with spines. 



Proartiiri. 

 aa. Palatoquadrate apparatus not articulated with the skull; no dorsal spines. Galei. 



Suborder PROARTHRI. 



(The Cestraciont Sharks.) 



This group is characterized by the articulation of the palatoquadrate 

 apparatus by an extensive surface with the preorbital regiou of the skull. 

 Vertebrte asterospoudylous. It consists of a single family, the Heteuo- 

 DONTiD.E, which, like the preceding families, possesses much interest to 

 pala'ontologists from its supposed relation to extinct forms, (t^p", before; 

 ufiBfiov, joint; Cestracion,is an old name, from Kiarpu, a pickax; the name 

 probably originally applied to Sjjhyrna.) 



Family VII. HETERODONTID^E. 



(The Bullhead Sharks.) 



Sharks with 2 dorsal fins, each provided with a strong spine; the 



first dorsal opposite the space between pectorals and ventrals; the 



second in advance of the anal. Body elongate, obtusely trihedral. 



