458 THE VOYAGE OF II. 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 

 paxillse 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 paxillse. 



The ambulacral tube-feet are large, and have a fleshy, centrally-invaginated, terminal disk. 



Colour in alcohol, a bleached vellowish 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 o- Fahr. 



Remarhs. — 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 paxillse, 

 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 



