290 
interradial plates they are rather distant on account of the faet 
that rounded, glassy grains are developed on the plates, the spinelets 
being thus placed in the interspaces between these glassy grains. 
(Fig. 8). The number of the spinelets is rather different according 
to the size oF the “paxillæ”; there are ca. 5 — 6 central and 10 —15 
marginal ones in the midradial plates, and about 
the same number also in the larger interradial 
plates. The madreporite is small, situated almost 
midway between the edge and the centre of the 
disk. There is a fairly distinet anal pore. 
The marginal plates are 8 to each side of 
arm, the outer one being still very small. They 
are rather lumid, separated by broad and deep 
furrows, and covered on the upper side by very 
short spinelets, not very closeset, as they are 
separated through glassy grains. On the low vertical sides the 
spinelets are somewhat coarser and more closeset, the glassy grains 
being here less numerous. The covering of the inferomarginal plates 
is like that of the superomarginals, only the spinelets on the ver¬ 
tical side slightly larger than those of the superomarginals. The 
unpaired marginal plate is of the same size as the adjoining 
marginals. — The larger of Benham’s specimens also had only 
8 marginals on each side of arm, while his smaller specimen had 
10 marginals. The terminal plate is fairly large, somewhat triangular. 
The armature of the adambulacral plates is somewhat difficult 
to make out on account of the poor preservation, but it appears 
that there are two subequal furrow spines, except on the two-three 
proximal plates, which have three, or even four of them. Apparently 
there are 3—4 pairs of outer adambulacral spines. The large, 
unpaired jawspine is somewhat compressed. 
The plates of the interradii are arranged in two-three regular 
series, parallel to ihe adambulacral plates. The proximal ones are 
distinetly larger than the distal ones. They are sparsely covered 
with small spinelets, separated through small glassy tubercles. No 
pedicellariæ are found. 
The present species differs very conspieuously from Peridontaster 
Grayi, especially in the covering of the paxillæ and of the marginal 
plates, which in the latter species consists of closeset grains; the 
Fig. 8. Peridontaster 
Benhaini. Dorsal 
plate; showing glassy 
grains among the 
spinelets. 2 «/i. 
