FAMILY SQUALID. 359 
GENUS SPINAX. Cuvier. 
A sharp robust spine in front of each of the two dorsals. Temporal orifices. No anal fin. 
Teeth in several rows, small and cutting. First dorsal in advance of the ventrals. Bran- 
chial apertures all in front of the pectorals. 
THE SPINOUS DOG-FISH. 
SpinaX ACANTHIAS 2 
PLATE LXIV. FIG. 210. 
Spinar acanthias, Picked Dog-fish. Storer, Massachusetts Report, p. 187, 
Characteristics. Slate-color above ; dull white beneath. Upper lobe of the tail subtruncate 
behind. Length one to three feet. 
Description. Body elongated, cylindrical. Snout produced, subconic, flattened above, and 
in the living fish translucent. Surface with asperities directed backwards. A slightly ele- 
vated line on the back between the dorsals, and becoming effaced on the nape. Lateral line 
nearly medial, straight, but sinuous on that portion of the tail included between the lobes and 
the caudal. Eyes large, oblong. Temporal orifices large, and closed from before by a strong 
cartilaginous valve ; they are placed a short distance behind the eyes, and in the plane of the 
upper margin of the orbits. Nostrils double, transversely beneath the snout, and rather nearer 
the eyes than to the tip of the snout; the internal largest. Mouth, when closed, semi-circular ; 
when expanded, nearly round. Three rows of small trenchant triangular teeth in the upper 
jaw, with smooth edges; two rows in the lower jaw, of similar teeth, and the rudiments of 
a third exterior row: the points of all the teeth diverge from the centre of the jaw outwardly. 
Numerous mucous orifices about the head and snout. Length of the head, measured to the 
first branchial aperture, to the length of the body, as one to six and a half nearly. 
The first dorsal broad and quadrilateral, convex in front, slightly concave on its upper mar- 
gin, straight on its posterior margin, pointed, and almost parallel with the line of the back. 
Imbedded in its anterior base is a robust slightly recurved spine, about two-thirds of the ante- 
rior height of the fin, white at the tip, and transversely striate with umber at the base. The 
second dorsal, which arises on the anterior part of the posterior third of the animal, is smaller 
than the first, but similar in shape with the upper margin, more deeply excavated above, and 
finely pointed behind ; the spine on its anterior portion, longer than the first, and nearly equal 
in height to the anterior part of the fin. Pectorals large and long, placed low down; its tip 
receiving a point nearly beneath the first dorsal spine. Ventrals quadrilateral, arising mid- 
way between the termination of the first and the commencement of the second dorsal, concave. 
Caudal fin with unequal lobes; the upper elongated, broad, subtruncate at the extremity ; 
the lower short and rounded. 
