HISTORY OF THE FISHES OF MASSACHUSETTS. 243 



Carcharias obscurus, Storei 



The Dusky Shark. 

 (Plate XXXVI. Fig. 2.) 



Snuahis obscurus, Dusky Shark, Lesueur, Acad. Nat. Science 1, p. 223, pi. 9. 

 Carcharias obscurus, " " Storer, Report, p. 184. 



" " " Bost. Journ. Nat. Hist., n. p. 558. 



" " Dekat, Report, p. 350, pi. 61, fig. 201. 



" " Storer, Synopsis. 



Color. Above, a dark yet vivid blue, somewhat banded by lateral lines, yet gradually 

 passing into the pure white of the abdomen ; this tinge of the back extends low upon 

 the sides. Upper part and sides of head, as well as caudal and most of dorsal fins, of a 

 delicate steel color with coppery reflections. Pectorals above, very dark green ; beneath, 

 a dull white. Posterior border of dorsals covered with a black mucous slime. Pupils 

 dark brown, irides golden. 



Descrijrtion. Body tapering gently posteriorly ; its greatest depth, midway between 

 the pectorals and the first dorsal fin, equal to a little more than one seventh the entire 

 length. Head elongated, sharp, flattened above and below. Snout throughout studded 

 with mucous pores arranged in fines or at random, some of which are very large. The 

 length of the head is equal to little more than one sixth the length of the body ; its 

 greatest depth is about one third its length, and nearly equal to its greatest width. 

 Eyes large ; their longest diameter, the longitudinal, equals about one quarter the dis- 

 tance between them. Nostrils situated on the outer edge of the lower surface of the 

 head, not quite midway between the eyes and end of the snout, nearer the eye, double ; 

 the anterior and outer, a narrow slit, entering downwards and inwards ; the posterior, 

 nearly circular. Mouth not very large ; the outer edge of the upper jaw just beneath 

 the centre of the eye ; its outer angle about one third the distance between the eye and 

 pectorals. Both jaws armed with short, triangular, and serrated teeth ; those in the 

 upper jaw curved backwards ; in each jaw a single row behind, a double row in front. 

 Branchial apertures, five, comparatively small ; the posterior two just above the anterior 

 margin of the pectorals. 



