350 NEW-YORK FAUNA. 



The first dorsal with a narrow base, rounded in front ; its margin concave, and acutely 

 elongated behind. It arises over the posterior part of the base of the pectorals, with its base 

 and extreme height 2' 7 and equal. The second dorsal rhomboidal, acutely pointed behind. 

 The pectorals, although rising from a narrow base, may be considered as broad fins ; four 

 inches long, with a base of one incii and a half and two and a half inches along the posterior or 

 lower margin. Ventrals small and obliquely truncated, with two pointed appendices beneath, 

 0'7 long. Anal deeply notched ; its upper lobe longest, pointed ; the anterior lobe rounded. 

 Tail elongated, six inches long, with two lobes, the spinal column running through it ; the 

 upper lobe subequal throughout, slightly enlarged at the tip, and extending a little beyond the 

 vertebrse ; lower lobe triangular, two inches high, then suddenly diminishing along the under 

 side of the tail, suddenly enlarging near the tip, and forming a third lobe. 



Color. Slate-blue on the upper part of the head, body and superior fins. The same color, 

 but a shade lighter, extends over the upper part of the pectoral and ventral fins. All beneath 

 whitish ; occasionally cinereous. 



Length, 25 '0. Extreme depth, 3'0. 



This species is frequently taken in our waters, and along the coast to New-Hampshire. I 

 have altered the name of glaucus, as it is the same with that employed by Rondeletius and 

 Yarrel. I should be inclined to consider this and the obscurus of Lesueur as identical, were 

 it not for the teeth, which he represents in his plate as having rounded shoulders. They are 

 at all events closely allied species. 



THE DUSKY SHARK. 



Carcharias obscurus. 



plate lxi. fig. 201. 



Dusky Shark, Squaltu obscuna, Lesdkde, Ac. Nat. Sciences, Vol. J, p. 223, pi. 9. 



Characteristics. Pectorals long, narrow, falciform. Ventrals subquadrangular, with no 

 pointed process behind. Snout flat and rounded. 



Description. Head flat and broad ; snout sharp-edged, rounded, and wide at the end. Eyes 

 lateral, large, orbicular ; pupil transverse, narrow, with a nictitating membrane arising from 

 below. Branchial apertures unequal ; the first very large, the last very small, and placed 

 above the origin of the pectoral fin. Nostrils oblique, and partially covered by a short pointed 

 appendage on the margin, near the end of the snout. Tail rounded, strong, with a falciform 

 fin, terminating in a distinct triangular lanceolate lobe. The lower lobe of the fin short and 

 rounded. Tail with a carina, undulated above, and slightly notched at the base. Ventrals 

 small, subquadrangular, without posterior processes. 



Color. Dusky, with a white spot on each side of the space between the eyes and pectoral 

 fins. 



Length . 



