28 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 



larger tliaii tlio second, botli similar to tbe anal ; pectoral iiiis short, 

 obtuse, or truucate ; color gray. L. 4 to G feet. 



A small voracious sharlc with very sharp teeth, rather common on 

 our Atlantic coast. 



{Si/uahifi amcrkunnii Mitcli. Traus. Lit. &, Phil. Soc. 1814, i, 48^5: Squalus litioralh 

 Mitcli. Am. Monthly Mag. ii, 1818,3^28: Carf/wr/rts ^W.se».s Storer, Fishes Mass. 217: 

 Odonlaspls americiuius Giiuther, viii, 392: Eugomphodus Uttondh Gill, Proc. Ac. Nat. 

 Sci. Phila. 18{i4, 260.) 



Family XL— LAMNID^. 



[The Porbeagles.) 



Sharks of large size, with the body stout, the mouth wide, with large 

 teeth, and the caudal tin lunate, the two lobes being not very unequal, 

 the upper lobe strongly bent upward ; caudal peduncle with a keel on 

 each side ; gill-openings wide, all in front of the pectorals, entirely lat- 

 eral, not extending under the throat ; first dorsal large ; jiectorals large ; 

 ventrals moderate ; second dorsal and anal very small; a pit at the root 

 of the caudal; spiracles minute or absent. Genera 3; species 6 or 

 more. Those inhabiting our coasts have been much confused by authors. 

 {I'jamnidw, part, (riinther, viii, 389-392.) 



* Teeth with entire edges. 



((. Teeth without basal cusps, long, liexuous, prismatic, and acute ... IstiRUS, 26. 

 (Id. Teeth, or most of them, with a small cusp on each side at base, compressed, 



.sharp, and somewhat triangular Lamna, 27. 



** Teeth with seiTated edges, compressed, and triangular in form . . Carchakodon, 28. 



26.— ISURUS Rafinesqne, 1810. 



Porbeagles. 



{Oxyrlmia Ag.) 



(Rafinesqne, Caratteri di Alcuni Nuovi Geueri : ty]ie Lsurus ojDjrhj/nchus 'Raf.=Oxijrhina 

 upallanzanii Bon.) 



Snout rather long and iiointed ; first dorsal and pectorals large ; sec- 

 ond dorsal and anal very small; caudal i)eduncle slender; teeth long, 

 lanceolate, with sharp entire cutting edges and no basal cusps, (•'''^■"r, 

 equal; oupa^ tail; the two lobes of the tail being nearly equal, as in all 

 the members of this family.) 



* First dorsal inserted entirely l)ehiud jjcctorals, nearly midway between pectorals and 



ventrals. {l8uropms QW\.) 



35. I. g^lnueus (M. *fc H.) Jor. &, Gilb.— J/ac7,;frc7 Shark. 



This species, if really occurring on our coast, will be known from the 

 other Isuri by the position of the dorsal, which is distinctly behind the 



