Jordan and Evermann. Fishes of North America. 47 



both similar to the anal ; pectoral fins short, obtuse or truncate. Color 

 gray. L. 5 feet. A small voracious shark with very sharp teeth, rather 

 common on our Atlantic coast, especially between Cape Cod and Cape 

 Ihitteras, said to differ from the European C. taurus in its more anterior 

 dorsal; the two species need further comparison, (littoralis, pertaining 

 to the shore.) 



tiiudhts iiHieriannu, MIT-CHILL, Trans. Lit. and Phil. Soc., 1815, i, 483, New York, (not of Shaw). 

 Squidm littoralis, and S. macrodw, MITCHILL, Am. Monthly Mag., u, 1818, 328, New York. 

 Carcliariitx (/risi-ns, AYRES, Bost. Jour. Nat. Hist., 1844, 288, Long Island. 

 <),lnt<i.pisaineri<-mins, GuNTHER, Cat., VIII, 392,1870. 

 Etujomphodus littoralis, GILL, Proc. Ac. Nat. Sci. Phila., 1864, 260. 

 Carcharias americanus, JORDAN & GILBERT, Synopsis, 27,1883. 



Family XV. LAMNID.E. 

 (THE MACKEREL SHARKS.) 



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

 teeth, and the tail slender, the caudal fin lunate, the 2 lobes being not 

 very unequal, the upper lobe strongly bent upward; caudal peduncle 

 with a strong keel on each side; gill openings wide, all in front of the 

 pectorals, entirely lateral, not extending under the throat; first dorsal 

 large; pectorals 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, besides numerous fossil species. In this family the 

 dentition, as well as the muscular system, reaches its highest degree of 

 specialization. (LAMNID.E, part, Giinther, Cat., vni, 389-392.) 



a. LAMNIN^E. Teeth Blender and sharp, with entire edges. 



b. Teeth without basal cusps, long, flexuous, and acute. ISURUS, 32. 



bb. Teeth, or most of them, with a small cusp on each side at base, compressed, sharp, and 



somewhat triangular. LAMNA, 33. 



aa. CARCHARODONTIN.E. Teeth with serrated edges, compressed, and triangular in form, without 



basal cusp. CARCHARODON, 34. 



32. ISURUS, Rafinesque. 



Taurus, RAFINESQUE, Caratteri di Alcuni Nuovi Generi, 11, 1810, (oxyrhynchus). 

 Oryrhina, AGASSIZ, Poissons Fossiles, in, 276, 1836, (spattanzanii = oxyrhynchus). 

 Isuropsis, GILL, Ann. Lye. Nat. Hist. N. Y., vni, 153, 1801, (glaucus). 



Snout rather long and pointed ; the body formed much like that of a 

 tunny or mackerel ; first dorsal and pectorals large; second dorsal and 

 anal very small: caudal peduncle slender; teeth long, lanceolate, with 

 sharp entire cutting edges and no basal cusps. (Zcrof, equal; ovpu, tail; 

 the two lobes of the tail being nearly equal, as in all the members of this 

 family.) 



ISTJROPSIS, (iero5, equal ; ovpa, tail; o//i?, appearance): 

 a. First dorsal inserted entirely behind pectorals, nearly midway between pectorals and 



Tentrals. 

 b. Height of dorsal 1% in head; pectoral as long as head. DEKAYI, 65. 



ISURUS: 

 aa. First dorsal inserted close behind pectorals. OXYRHYNCHUS, 06. 



