FAMILY SQUALIDiE. 359 



GENUS SPINAX. Ciivirr. 



A sJiarp robust spine in front of each of the ttvo dorsals. Temporal orifices. No anal fin. 

 Teeth in several roivs, small and cuttins;. First dorsal in advance of the ventrals. Bran- 

 chial apertures all "in front of the pectorals. 



THE SPINOUS DOG-FISH. 



Si'iNiX acanthus'? 

 PLATE LXIV. FIG. 210. 

 Spinax tiranlhias, Ptcktd Dp^-ftsh. STOKER, Massachusetts Report, p. 187. 



Characteristics. Slate-color above ; dull white beneath. Upper lobe of the tail subtnincaie 

 behind. Length one to three feet. 



Description. Body clonfi;atcd, 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 ; ihcy arc placed a short distance behind the eyes, and in ihe 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 ilrst, and nearly c(|ual 

 in height to the anterior part of the fin. Pectorals large and long, placed low down ; its tij) 

 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, subtnincaie at the extremity: 

 the lower short and rounded. 



