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 inch and a half and two and a halfinches 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 Jongest, 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 
vertebre ; 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 Lesucur 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. 
Carcuarias OBSCURUS. 
PLATE LXI. FIG. 201. 
Dusky Shark, Squalus obscurus. Lesueur, Ac. Nat. Sciences, Vol. 1, p. 223, pl. 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 Jobe. The lower lobe of the fin short and 
rounded. ‘Tail witha 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 ‘ 
