368 U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



elevated at the inner part than at the outer; the inner part having, moreover, a longitudinal keel, the outer part constituting a 

 rounded process, directed towards the point of the tooth. First dorsal fin placed between the pectorals and the ventrals; the 

 second between the ventrals and the caudal fin. Upper lobe of caudal larger than the lower; sometimes a caudal groove or 

 furrow is observed. In the male a movable spine or thorn, bent upon its apex, may be seen at the outer edge of the extremity 

 of the ventral appendages. The scales are s ub- cord i form, posteriorly acute, with one or several keels. 



SYN.- Jlcanthias, Risso, Hist. nat. Eur. nierid. Ill, 1826, 131 MULL. & HENLE, Syst. Beschr. Plagiost. 1841, 83. 

 STOKER, Synops. 1846, 254. BUM. Ichthyol. analyt. 185G, 133. 



Of all the genera of Spinacidae, the genus Spinax is the one to which Acantldas bears the 

 closest affinities, the latter having been admitted by comparatively few writers. 



ACANTHI AS SUCKLII, Grd. 



SPEC. CHAR. Head constituting somewhat more than the sixth of the entire length. Snout very much depressed and 

 elongated ; nostrils nearer its apex than the angle of the mouth. Eyes large, elliptical, situated immediately in advance of the 

 mouth. Anterior margin of first dorsal fin nearly equidistant between the pupil and the anterior margin of the second dorsal. 

 A shallow caudal groove along the base of the upper lobe of the caudal. Dark greyish, with a few light irregularly scattered 

 spots. 



SYN. Spinax (rfcanthias) suckleyi, GRD. in Proc Acad Nat. Sc. Philad. VII, 1854, 196. 



We have examined one specimen of this species measuring nearly two feet and a half in total 

 length, the head forming a little more than the sixth part of it. The body is very much 

 elongated, slender, and gradually tapering posteriorly. The snout is very much depressed, 

 elongated, and, when viewed from above, sub-conical in its outline. The nostrils consist of a 

 circular free aperture, and of a transverse split continuing it inwardly. At the anterior edge 

 of this split may be observed an elongated flap, tapering and rounded off, which overlaps 

 the split at the inner edge of the circular aperture ; the rest of the anterior edge of the split, as 

 well as the entire posterior edge, exhibits a narrow, thin membranous expansion more developed 

 at the posterior edge than at the anterior. The nostrils themselves are somewhat nearer the 

 apex of the snout than the angles of the mouth. The latter is large ; measured from angle to 

 angle, it is a little less than the rostral distance from the middle of the anterior jaw forwards. 

 The cartilaginous fold of the posterior (inferior) angle is shorter but thicker than the outer one 

 at the anterior (superior) lip. The inner one at the same anterior lip is very slender and mostly 

 covered by the outer one. The eyes are very large, elliptical, their longitudinal diameter 

 entering about four times along the distance between the apex of the snout and the spiracles ; 

 they are situated immediately in advance of the mouth. A longitudinal groove may be seen 

 at the anterior and at the posterior rim of the orbit. The spiracles being somewhat oblique 

 and transversely elongated. The branchial apertures increase in size from forwards backwards; 

 the fifth, which is conspicuously larger than the rest, is placed immediately in advance of the 

 anterior margin of the pectorals. 



The dorsal fins are of moderate development, higher than long, and superiorly concave. The 

 spine at the anterior margin of the second dorsal is larger than that of the first dorsal. The 

 anterior margin of the latter fin is nearly equidistant between the pupil and the anterior margin 

 of the second dorsal, which, in its turn, is nearer the anterior margin of the first dorsal than 

 the extremity of the caudal fin. The upper lobe of the caudal is sub-lanceolate, posteriorly 

 rounded off; the lower lobe is much deeper, sub-triangular, and concave upon its inferior 

 margin ; the origin of either lobe is even. A shallow caudal groove may be observed along 

 the base of the upper lobe. The ventrals are small, appearing more like a marginal expansion 

 of the ventral appendage than fins properly so called. They are rounded off exteriorly and 

 linear posteriorly. The anterior portion of their insertion is nearer the extremity of the caudal 



