REPORT ON THE OPHIUROIDEA. 193 



arm plates pentagonal, with a strongly curved outer side, and lateral and inner lateral 

 sides re-enteringly curved ; length to breadth (third plate) - 8 : 1. Upper arm plates 

 broad transverse diamond-shape, widely separated. Side arm plates stout and prominent, 

 meeting freely above and below. Disk densely set with coarse stumps, which bear a 

 crown of strong thorns and are also usually thorny on their sides. Eadial shields and 

 scaling hidden, except the outer tips of the former. Seven or eight slender, feebly 

 thorny arm spines ; the upper one longest (3 mm.), the three lowest about equal. 

 Tentacle scales long, large, and pointed. Colour in alcohol, grey. 



Station 3.— February 18, 1873 ; lat. 25° 45' N., long. 20° 12' W. ; 1525 fathoms. 



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

 The characters were, however, distinct. 



Ophiacantha cornuta, Lym. (PL XV. figs. 3-5). 



Ophiacantha cornuta, Lym., Bull. Mus. Comp. Zool., vol. v., part 7, p. 145, pi. x. fig. 2GG, 

 1878. 



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. 



(Type specimen from Station 171.) Diameter of disk 5 '5 mm. Width of arm with- 

 out 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 thau 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 having 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 millimetre, closely beset and partly obscured by little stumps con- 

 sisting of a slender trunk bearing a crown of six or eight minute thorns. Eight trans- 

 lucent 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 pro- 

 portionately larger, and stands below three very slender arm spines. Tentacle scale 

 flat, stout, pointed. Colour in alcohol, white. 



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

 spines, &c, 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), 



