232 THE VOYAGE OF H.M.S. CHALLENGER. 
mally placed spinelets really belongs to the true marginal series it is probable that the 
prominent and enlarged mouth-spine should be reckoned as the foremost of the actinal or 
superficial series. On the actinal surface of each plate is a longitudinal series of eight to 
twelve rather robust and conically pointed spinelets, parallel to the median suture; and 
an intermediate series, fewer in number and more widely spaced, between these and the 
marginal series. 
The actinal intermediate plates are confined to a very small area in the interradial 
region, but I am unable to say from superficial observation whether their arrangement 
presents any regularity or not. Hach of the plates bears two or three short, robust, conical 
tipped spinelets, which have a more or less marked tendency to form a group. 
The madreporiform body is entirely obscured by paxille. 
Colour in alcohol, a dirty greyish white. 
Locality.—Station 237. Off the coast of Japan, south of Kawatsu. June 17, 1875. 
Lat. 34° 37/0” N., long. 140° 32’ 0” EB. Depth 1875 fathoms. Blue mud. Bottom 
temperature 35°°3 Fahr. ; surface temperature 73°°0 Fahr. 
Remarks.—Psilaster gracilis has a very different facies from any of the other species 
described, and it is not without hesitation that I have included it in the genus. It is at 
once distinguished by its narrow subcylindrical rays and widely rounded interbrachial 
ares; by the papilliform covering of the marginal plates ; by the large inner pair of mouth- 
spines ; and by the general character of the actinal spinulation. 
5. Psilaster patagiatus, n. sp. (Pl. XLI. figs. 3 and 4; Pl. VII. figs. 11 and 12). 
Rays five. R=79 mm.; r=20 mm. R<4r. Breadth of a ray near the base 
(between the second and third supero-marginal plates), 19°5 mm. 
Rays elongate, broad at the base, and tapering continuously and gradually up to the 
extremity. General form comparatively flat and depressed. Abactinal and actinal areas 
subplane. Interbrachial arcs widely open and rounded. 
The abactinal paxillar area of the disk and rays is covered with numerous, rather large, 
distinctly spaced paxille. These are composed of very small, short, delicate, cylindrical 
spinelets, three to five or rarely more being central, and surrounded by a marginal 
circle of about a dozen; the latter, instead of radiating outward as usual in paxille, 
have a slight inclination inward, which gives the groups a more or less closed and highly 
characteristic appearance. By this means the papule, which are remarkably small, are 
all exposed to view. In some of the paxillee three or four of the central spinelets are 
slightly enlarged, and appear to form a pedicellarian organ. Along the margin of the area 
the paxille are arranged in very regular transverse series ; but there is no definite order 
along the median radial line or in the central area of the disk. 
The supero-marginal plates, thirty in number from the median interradial line to the 
