174 DISCOVERY REPORTS 



Description. The paxillae are low, flat-topped, spaced less than the diameter of the 

 crown of compactly placed short spinelets which form a co-ordinated group. Spinelets 

 15-30, usually 20-30, to a paxilla, slightly longer than the low tabulum which springs 

 from a 4-lobed base. Spinelets with 3 deeply excavated sides, broadening conspicuously 

 to a convex truncated summit beset with numerous points. Spinelets 0-3-0-4 mm. long 

 and not obviously bound together by membrane, although there is a very delicate 

 membrane at the base, continuous with the thin dermal investment of spinule. 



The abactinal plates are squarish with rounded corners and shallowly excavated sides. 

 They strongly overlap by these incipient lobes and the very small interstices accom- 

 modate a single papula. Plates form fairly regular transverse series, the regularity of 

 which is interrupted at midradial line. 



Madreporite 1-5 mm. in diameter, situated in middle of r and hidden by paxillae. 



Superomarginals alternate with inferomarginals. They are conspicuously larger than 

 adjacent small abactinals but on outer part of ray the difference is not so marked. The 

 crown does not extend above the level of the abactinal paxillae, although the spinelets 

 are slightly coarser and number about the same as on large abactinal paxillae (i.e. 20-30). 



Inferomarginal paxillae 20, conspicuously larger than the superomarginals, with 

 about the same number of still heavier spines which increase conspicuously in size from 

 the dorsal to ventral margin of tabulum. The inferomarginals have a shorter pedicel and 

 more compact appearance than in L. stellans. The largest spines are about o-6 mm. long, 

 while a few small ones from dorsal margin are as small as o-3-o-4mm. (Fig. E, 46). 



The actinal interradial area is well developed for so small a specimen, containing 3 

 chevrons of plates. The first series extends to end of ray. The plates on the disk have 

 6-9 divaricate spines on a slight convexity. Beyond the second or third inferomarginal 

 the plates become spaced and carry 3 or 4 spinelets, then 2, and finally only i. At 

 middle of ray there are 6 actinals to 3 inferomarginals. The second chevron does not 

 extend beyond the second inferomarginal; while the third consists of 3-5 plates adjacent 

 to the first inferomarginal of neighbouring series. 



Adambulacral furrow spines 5, 4, 3, 2 from base to end of ray. They are rather coarse, 

 subterete, round-tipped when covered with membrane. The 2 or 3 median are much 

 longer than the laterals of the comb and all are united by web to mid-height. Sub- 

 ambulacrals in a curved transverse series of 4 or 5 spines increasing in size from outer 

 to inner. The inner 2 or 3 are much coarser but not much longer than the median furrow 

 spines and are from i to i-2 mm. long (Fig. E, 4c). 



The oral plates are characteristic of Lophaster in form and armature ; marginal spines 

 6-8, webbed increasing in length to innermost, which, being slightly longer than sub- 

 ambulacrals, are the largest spines on body. Suborals 9 or 10 in two poorly defined 

 series adjacent to median suture and widely spaced from the marginal spines. 



Gonads interradial, opening on upper border of first superomarginal plate. There is a 

 slender calcified interbrachial pillar extending from odontophore to abactinal wall, but 

 no membranous septum joins this pillar to the wall of body at interbrachium, as in 

 Crossaster. There is no trace of the characteristic muscles of Myoraster. 



