36G THE VOYAGE OF II M.S. CHALLENGER. 



spinelet, the membrane mounting the base and causing it to appear very robust and broad. 

 There is thus a series of spinelets running parallel to the margin. One or two plates on 

 the inner part of the area bear a similar spine, but only one appears to be regular in 

 occurrence, and that is situated near the apex of the area. 



The abactinal area is covered with thick membrane, and although the individual plates 

 are indistinguishable, many of them appear to be comparatively large. They bear groups 

 of small, equal, robust, papilliform granules, scarcely worthy of being called spines ; and 

 these groups have an isolated appearance. Comparatively large, isolated, single papulae, 

 widely spaced, are distributed over the surface, excepting a narrow area along the median 

 radial and the median interradial lines ; along the outer part of the latter is a faiut 

 channel. 



The madreporiform body, which is small and circular, is situated about midway 

 between the centre of the disk and the margin. 



The anal aperture, which is large and conspicuous, is margined by small papilliform 

 spines. 



Colour in alcohol, bleached yellow, with a light brown shade in places. 



Locality. — " Porcupine " Expedition : 



Station 31. Between the north of Ireland and Eockall. Lat. 56° 15' N., long. 11° 25' 

 W. Depth 1360 fathoms. Bottom temperature 2°"9 C. ; surface temperature 13°"8 C. 



Remarks. — So far as I can judge from the short descriptions of the three 1 species 

 hitherto known, together with the figures of two of them, this form appears to me unques- 

 tionably different from any of them. 



Marginaster Jimbriatus differs from Margiuaster pectinatus, Perrier, in having groups 

 of granules on the abactinal plates ; and in the absence of the comb of spinelets on the 

 supero-marginal plates, which according to Perrier's description are present in Marginaster 

 pectinatus, and similar to those on the infero-marginal plates. The armature of the 

 adambulacral plates is also different, and the lineal series of spinelets on the actiual inter- 

 radial areas parallel to the margin are wanting in Marginaster pectinatus. 



Marginaster pentagonus, Perrier, differs in having the abactinal plates furnished with 

 spines disposed in irregular arcs on the margin of the plates ; in the large number of 

 spines which form the comb on the marginal plates (about ten) ; and in the armature of 

 the adambulacral plates. 



Marginaster echinulatus, Perrier, differs in the stellate form ; in the totally different 

 character of the adambulacral armature ; in the presence of two spines on each actinal 

 intermediate plate ; in havirig only a single row of papulse on each side of the median 

 radial line ; and in the peculiar form of the plates which occupy the median radial Hue (as 

 shown in the figure). 



1 Perhaps the starfish described by Gasco (Rendic. R. Accad. Set. Fis. e. Mat. Napoli, 1876, Anno sv., 

 fasc. 2, p. 9), under the name of Asteropsis capreensis, may ultimately prove to belong to this genus also. 



