38 THE VOYAGE OF H.M.S. CHALLENGER. 
Localities. —*“ Porcupine’ Expedition : 
Off Valentia. Depth 100 to 150 fathoms. 
Station 51 (“ Porcupine,” 1869). Inthe Faerée Channel. Lat. 60° 6’ N., long. 8° 14’ W. 
Depth 440 fathoms. Bottom temperature 5°°5 C.; surface temperature 10°99 C. (A 
single badly preserved specimen, which I refer with some doubt to this species.) 
Station 2 (“ Porcupine,’ 1870). South-west of the Scilly Islands. Lat. 48° 37’ N., 
long. 10° 9’ W. Depth 305 fathoms. Bottom temperature 14°°8 C.; surface temperature 
16°-2 C. 
Remarks.—This species is in many respects a near ally of Pontaster tenuispinus, but 
is readily distinguished by the small disk, by the short and regularly tapering rays, and by 
the broad border of the supero-marginal plates on the abactinal surface. It is further distin- 
guished by the character of the paxille, by the remarkably small spines on the supero- 
marginal plates, by the short and solitary lateral spines on the infero-marginal plates, by 
the character of the armature of the adambulacral plates, and by the absence of pedi- 
cellarize therefrom. The papularia and also the actinal interradial areas are different. 
5. Pontaster oxyacanthus, n. sp. (Pl. IX. figs. 1 and 2; Pl. XII. figs. 7 and 8). 
Rays five R=73mm.;7r=11 mm: R>65r. _ Breadth of a ray near the base, 
11 mm. 
Rays elongate, tapering continuously from the base to the extremity, the outer part 
narrow and attenuate, and of great flexibility; the outer part in the specimen under notice 
curled round with an abactinal recurvature. Interbrachial arcs well-rounded. Abac- 
tinal surface plane. Actinal surface subplane. Lateral walls of the rays comparatively 
high and vertical. 
The general paxille of the abactinal surface are comparatively small and simple, 
closely placed on the disk and inner part of the rays, but diminish greatly in size as they 
proceed outward, and are more widely spaced on the outer half of the ray. The crown 
consists of four to seven short, delicate, tapering spinelets, which radiate outward nearly 
horizontally, and appear to proceed almost from the centre of the tabulum. A few have 
a small central spinelet, more elongate and robust than the surrounding series. Upon the 
disk and at the extreme base of the rays a number of larger and specially-armed 
paxille are distributed amongst the general paxille above described. Each of these 
bears an elongate conical, tapering, robust, vertical spinelet, surrounded at the base 
by a ruff-like collarette of twenty or more minute ciliary thornlets. The central spine is 
powerful, and may measure 2 to 3 mm., but the length decreases as the paxille recede 
from the centre of the disk. The disposition of these armed paxillee is somewhat irregular ; 
they are, however, confined to a median radial area, and two or perhaps three irregularly 
