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. Each 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 paxillse. 



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" E. Depth 1875 fathoms. Blue mud. Bottom 

 temperature 35°'3Fahr. ; surface temperature 73°"0 Fahr. 



Remarhs. — 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 

 arcs ; 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. (PI. XLI. figs. 3 and 4; PI. VII. figs. 11 and 12). 



Pays five. R = 79 mm. ; r = 20 mm. R< 4 r. Breadth of a ray near the base 

 (between the second and third supero-marginal plates), 19 - 5 mm. 



Pays 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 paxillse. 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 paxillse, 

 have a slight inclination inward, which gives the groups a more or less closed and highly 

 characteristic appearance. By this means the papulae, which are remarkably small, are 

 all exposed to view. In some of the paxillse three or four of the central spinelets are 

 slightly enlarged, and appear to form a pedicellarian organ. Along the margin of the area 

 the paxillas 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 



