MUSEUM OF COMPAEATIVB ZOOLOGY. 145 



Seven or eight slender, feebly thorny arm-spines ; the upper one longest 

 (3 nun.), the three lowest about equal. Tentacle-scales long, large, and pointed. 

 Color in alcohol, gray. 



Station 3, 1530 fathoms, 1 specimen. 



The only specimen was a disk with the bases of the arms and a few arm- 

 spines. The characters were, however, distinct. 



Ophiacantha cornuta sp. nor. 



Plate X. Fig. 266. 



Special Marks. — Disk-scales distinct and rather large, closely beset with 

 small stumps, having a slender trunk bearing a crown of six or eight minute 

 thorns. Lowest arm-spine thickened and curved. 



Description of an Individual (Station 171). — Diameter of disk 5.5 mm. Width 

 of arm ^^•ithout spines 2 mm. Seven mouth-papillae to each angle, of which 

 the three innermost are long, cylindrical, and pointed ; the odd one at angle of 

 jaw being largest. Mouth-shields much wider than long, with a curve without 

 and an obtuse angle within ; length to breadth .6 : 1.2. Side mouth-shields 

 wide and stout, broadly joined within. Under arm-plates much wider than 

 long, slightly curved without, having a little peak within, and the very short 

 lateral sides re-enteringly curved ; length to breadth .6 : 1.2. Upper arm- 

 plates small, much wider than long, almost of a transverse diamond-shape, 

 and lower than the ridge of the side arm-plates, which are large, meeting 

 broadly above and below, and have an unusually narrow projecting spine-ridge 

 continuous over the top of the arm. Disk, including radial shields, covered 

 by distinct imbricated scales, two or three in the length of a mm., closely beset 

 and partly obscured by little stumps consisting of a slender trunk bearing a 

 crown of six or eight minute thorns. Eight translucent arm-spines, all sharp 

 and strongly thorny, except the lowest, which is thickened, curved, and slightly 

 rough. Towards end of arm this spine is more curved and proportionately 

 larger, and stands below three very slender arm-spines (PI. X. Fig. 266). 

 Tentacle-scale flat, stout, pointed. Color in alcohol, white. 



This specimen was plainly not fully grown, and was imperfect by loss of 

 some arm-spines, etc., but the adult does not probably differ much, while the 

 hooked lowest arm-spine and character of disk mark it well as a species. A 

 young individual (Fiji Islands), with a disk of 3 mm. and arms 14 mm. long, 

 presented no variations beyond those of age, except that the lowest arm-spine 

 was rather less curved ; there were four spines besides this, the uppermost 

 being sometimes as long as 1.7 mm. 



Station 170, 520 fathoms. Station 171, 600 fathoms. Fiji Islands^ 520 fathoms. 



