220 THE PLAGIOSTOMIA. 



ACANTHIDIUM HYSTRICOSUM. 



Plate 11, fig. 5-8. 



Acanthidium hystricosum Gabman, 1906, Bull. M. C. Z., 46, p. 206. 

 Centrophorus hystricosus Regan, 190S, Ann. mag. nat. hist., ser. S, 2, p. 51. 



Sub fusiform, slender, compressed, depth nearly one eighth of the total 

 length. Head about one fourth of the total, depressed, flattened on the crown. 

 Snout elongate, broad, blunt at the end, narrowing in front of the nostrils. 

 Width of nostrils about half their distance apart, or one thud of that from the 

 end of the snout; valves narrow, with a short angular lobe across the middle of 

 the nostril and another smaller one a short distance farther inward. Eye large, 

 length of orbit little more than half of the distance from the end of the snout. 

 Mouth large, width less than half of the preoral length, with a deep straight. 

 groove and with labial folds at each angle, upper fold half the length of the jaw, 

 lower shorter. Teeth §jj; upper little narrower, cusp triangular, roof-shaped 

 in transsection, erect near the middle of the mouth, more oblique laterally; lower 

 much inclined toward the angles, cutting edge nearly horizontal, a deep notch 

 on the outer edge. Spiracle large, as wide as the first gill opening, above the level 

 of the eye and less than its width farther back. Gill openings in front of the 

 pectorals. Spine of first dorsal short, hardly half exposed, equidistant from orbit 

 and the spine of the second dorsal; base without the spine about half the length 

 of the head, nearly equal the interdorsal space; fin low, upper margin a low arch, 

 hind angle much produced. Second dorsal higher, base about two thirds as 

 long as that of the first, distance of base from supracaudal half their distance 

 apart, spine strong nearly as tall as the fin, rising little behind a vertical from the 

 axils of the ventrals, end of fin reaching the origin of the caudal. Ventrals small, 

 bases almost entirely in front of the origin of the second dorsal, bases about 

 half as long as their distance from the subcaudal. Pectorals moderate, sub- 

 truncate on hind margin, inner angle shorter, not reaching quite to the origin 

 of the first dorsal, or little more than halfway to a vertical from the dorsal spine. 

 Scales larger than those of .4. rostralum, pedicellate with radiate base and with 

 three sharp slender cusps at the summit each bearing a keel on its outer side, a 

 fourth erect cusp frequently occurring above the peduncle. 



Dark brown, little lighter below; inside of mouth, gill openings, and nostrils, 

 and edges of fins blackish. 



Total length 36|, snout to tail 24j, snout to dorsal spine, loj, snout to 

 pectoral 85, snout to mouth 5, and caudal fin 8 inches. 



Sagami Sea, Japan. Alan Owston. 



