458 THE VOYAGE OF H.M.S. CHALLENGER. 
The adambulacral plates are large and their armature consists of two series of spines. 
(1.) A furrow series of five short, robust, rather broad, slightly compressed, skin-covered 
spinelets, united by a membranous web at their base, and forming a usually vertically 
disposed semicircular comb, (2.) On the actinal surface of the plate is a transverse lineal 
series of three, or occasionally four large, conical, skin-covered spinelets, which decrease 
in size as they recede from the furrow. 
The mouth-plates are rather elongate, and with their armature have the appearance 
of an elongate pointed scoop. Their armature consists of a marginal series of ten spinelets 
on each plate. The innermost is rather longer than the others, the third and succeeding 
spinelets, which are subequal in length, are rather shorter than the second; all are united 
for fully two-thirds of their length by a membranous web. The innermost spinelet on 
each plate has rather an isolated appearance from the rest, and these two spinelets of the 
united pair of plates being close together give a characteristic appearance to the mouth- 
armature of this species. On the actinal surface of each plate is a curved series of five or 
six robust, conical, skin-covered spinelets, which diminish in size as they recede from 
the mouth. 
In the actinal interradial areas of the disk there are three or four series of small 
actinal intermediate plates, which bear small paxilliform groups of four to six short, equal 
spinelets; the innermost series extends to nearly midway along the ray, but the others do 
not pass beyond the base of the ray. 
The madreporiform body, which is small and inconspicuous, is situated rather nearer 
the centre of the disk than midway between that point and the margin. Its surface is 
not convex, the striations are rather coarse, and its margin is surrounded by five or six 
paxillee rather larger than the neighbouring ones. 
The anal aperture is distinct and subcentral. There is no modification in the size or 
character of the neighbouring paxille. 
The ambulacral tube-feet are large, and have a fleshy, centrally-invaginated, terminal disk. 
Colour in alcohol, a bleached yellowish white. 
Locality.—Station 170. North of the Kermadec Islands. July 14, 1874. Lat. 
29° 55’ 0” S., long. 178° 14’ 0” W. Depth 520 fathoms. Volcanic mud. Bottom 
temperature 43°°0 Fahr.; surface temperature 65°°0 Fahr. 
Remarks.—This species is distinguished from all other forms by the shape of the rays, 
by the sloping ravine on the disk at their base, by the character of the abactinal paxille, 
and by the armature of the adambulacral plates and mouth-plates. 
Genus Lophaster, Verrill. 
Lophaster, Verrill, Amer. Journ. Sci. and Arts, 1878, 3rd ser. vol. xvi. p. 214. 
Lophaster was hitherto known only from the North-Atlantic area. The Challenger 
obtained examples of a form which I consider referable to the genus from the South 
