206 bulletin: museum of comparative zoology. 



distinguished by difterences in rostral lengths, in the teeth, in the shapes, 

 positioiis, and lengths of the fins, in the scales, colors, etc. Generically 

 they agree in the characters of the head, the greatly produced snout, 

 large eyes, in nostrils, teeth, and spiracles, in the characters of the fins, 

 and in general shapes. In the scales they are farther than A. calceus 

 from Centrophorus, though like that species, their scales have slender 

 peduncles and are erect, but each has three slender, distinct, and sharp 

 cusps, without the web-shaped connections between their bases. On 

 the inside of the valves the spiracles are provided with ridges like the 

 gill laminae ; in front of the valve there is a blind cavity or chamber, 

 extending forward, like that of Centroscymnus, but of much less extent, 

 or that of Centrophorus. The inner angles of dorsals and ventrals are 

 much produced ; those of the pectorals are short. 



Acanthidium rostratum, sp. nov. 



Rather more compressed in body than the other species of this genus. Dorsal 

 spines strong, moderately exposed. Base of first dorsal in the forward half of the 

 total length ; inner angles of dorsals greatly, and those of the ventrals moderately 

 produced ; inner angle of pectoral little longer than outer, not produced in a point; 

 base of first dorsal about two fifths of its distance from that of the second, base of 

 second dorsal little more than that of the first ; end of base of ventral nearly reach- 

 ing a vertical from the second dorsal spine. Teeth -|§ ; upper with a notch at each 

 side of the cusp, which latter is oblique and becomes more so toward the angles of 

 the mouth ; lower with cutting edges very oblique, approaching a horizontal. Upper 

 labial folds hidden in the deep oblique grooves, half or more of each of which is in 

 front of the angle ; lower folds long, more than half as long as the jaw. Spiracle 

 large, above the level of the eye and one diameter farther back ; valves with small 

 ridges ; prevalvular chamber of moderate extent. Scales minute, with erect slen- 

 der peduncles, and slender spine-like cusps, each of which is surmounted by a sharp 

 longitudinal keel. 



Light brownisli or grayish brown, greenish or olive in life ; lighter beneath ; lit- 

 tle darker on back, top of head or tail ; whitish on hind and inner margins of dor- 

 sals, pectorals, and ventrals. 



Total length, 34 inches. 

 No. 1047, Mus. Comp. Zobl. 

 Hab. Suruga Gulf, Japan. 



Acanthidium hystricosum, sp. nov. 



Head nearly one fourth, tail one third, and caudal fin two ninths of the total 

 length. Middle of the total length in the middle of the base of the first dorsal, in- 

 cluding the spine. Teeth f f , compressed ; upper with narrow triangular cusps, which 

 are triangular also in cross section, erect near the symphysis, little oblique toward 

 the angles of the mouth ; lower with cusps directed toward the corners of the 

 mouth so much that each cutting edge is almost parallel with the edge of the jaw, 



