250 



BULLETIN OF THE BUREAU OF FISHERIES. 



Fig. 5.— Denticles. Ciiliilus rctifer, 16.7 cm. long, from Fish Hawk station 7315. Gulf Stream, oft Cape Lookout, N. C. 



Family CARCH.\RHINID/E. The requiem sharks. 



KEY TO THE GENERA. 



a. .Spiracle absent; lower teeth narrower than upper. 



b. Labial folds at angles of mouth ■well developed, extending along both jaws; teeth entire, oblique, 



notched Scoliodon . 



bb. Labial folds rudimentary; teeth erect and entire or serrated, some or all, on bases and cusps, 

 c. Teeth without serrations, slender, erect, sharp-pointed; upper teeth slightly larger. .Aprionodoti. 

 cc. Teeth of upper jaw serrate on basal shoulders only; lower teeth entire, slenderer, erect. 



Hypoprion. 

 ccc. Teeth serrated, some or all, on bases and cusps; teeth in upper jaw in most species more 



broadly triangular than those in Aprionodon or Hypoprion Carcharhinus . 



aa. Spiracle present, minute; teeth large, coarsely serrate, alike in both jaws, notched on outer margin; 

 labial folds at angles of mouth well developed GaUoccrdo. 



Genus SCOLIODON MUller and Henle 



8. Scoliodon terrte-novae (Richardson). Sharp-nose; sharp-nosed shark; dog shark. 



Scoliodon terrce-TUfv<e, Jordan and Gilbert. 1.S79. p. 388; Linton, 1905, p. 342; Smith, 1907, p. 34; Coles, 1914, p. 90. 

 Carcharhinus terrc^ncnuB, Jordan. 1886. p. 26; Jenkins, 1887, p. 84. 

 Carcharinus terrte-novtE, Wilson, 1900. p. 355. 

 Scoliodon tcrranov<r, Gudger, 1910, p. 399. 



26 . 



Teeth. — Teeth in — rows, oblique, compressed, broad-based, without serrations, each with a single 



cusp inclined toward the angle of the mouth, and a deep notch on posterior margin below the cusp; 

 teeth at symphysis of each jaw slightly smaller; median row in upper jaw and two rows at symphysis 

 of lower jaw erect; bases of teeth in upper jaw higher and cusps broader than in lower jaw; toward the 

 angles of the mouth the inclination of cusps falls, the anterior margin being almost horizontal in the 

 teeth at the angles; near front of mouth, the tips of the cusps are slightly bent toward symphysis, the 

 anterior margin being slightly concave; tliis character is more pronounced in teeth of lower jaw; near 

 angles of mouth, anterior margin straight. 



Denticles. — The denticles are three-keeled, very small in size, being about 0.17 by 0.17 mm. in a 

 shark 6 r cm. long, subequal, slightly overlapping; keels low but distinct, interspaces relatively flat, 

 not deeply concave; lateral keels intramarginal : apical margin of denticle with three acute-angled pro- 



