302 THE VOYAGE OF H.M.S. CHALLENGER. 
subcylindrical, and slightly tapering, radiate slightly apart, and their base line forms a 
gentle curve; the outermost spinelet at each extremity of the series is smaller than the 
others, the adoral one being the smallest, often almost aborted, and has the appearance of 
being placed rather far back on the plate. External to the furrow series is an outer series 
of four or five spinelets, which are much more robust, subpapilliform, slightly compressed, 
and stand in an oblique line which is farthest from the furrow adorally. The second spine 
from the aboral extremity of the series is the longest, and the most adoral the shortest, 
the intermediate spines forming a graduating series. External to these spinelets is a lineal 
series running parallel to the furrow, of four or five short papille, scarcely distinguishable 
from the miliary granules of the actinal intermediate plates. 
The actinal interradial areas are paved with comparatively large intermediate plates, 
which are consequently few in number; they do not vary greatly in size, and most are 
subrectangular or subrhomboid in shape, though a few are irregular. All have a series of 
small papilliform granules arranged round their margins, and a few similar papille widely 
spaced on the surface of the plate. Most of the plates in the series adjacent to the adam- 
bulacral plates bear one of the entrenched pedicellarize, but the other intermediate plates 
appear to be devoid of them, excepting perhaps a solitary one rarely. 
The mouth-plates are small, elongate, and narrow. They bear a series of about ten 
spinelets on the margin bordering the furrow, which increase in robustness as they proceed 
inward, the innermost being flattened into a broad knife-like appendage, with the thin 
edge placed in the direction of the ray. On the actinal surface of the plate a series of 
spinelets runs parallel to the median suture; they increase in length as they proceed in- 
ward, the outer ones being papilliform granules. Five small papilliform spinelets border 
the margin adjacent to the adambulacral plate, and a transverse or diagonal series of three 
short cylindrical spinelets proceeds from near the termination of the latter series at the 
furrow, across the surface of the plate, towards the longitudinal series adjacent to the 
median suture. One to three small -papilliform granules may also be present on the 
enclosed area on the outer half of the plate. 
The paxille of the abactinal area are tabulate, hexagonal, and distinctly separate in the 
radial areas, whilst those of the small triangular interradial areas are square or subrhom- 
boid and closely placed. The median radial line is occupied by a regular longitudinal 
series of hexagonal paxille, slightly larger than the rest, and with their transverse 
diameter a little greater than the longitudinal. On reaching the base of the ray these 
paxille lose their hexagonal form, become rectangular, and, gradually diminishing in size, 
do not extend beyond the middle of the ray, the supero-marginal plates of the two 
opposite sides of the ray uniting in the median abactinal line along the outer half of the 
ray. There are three parallel longitudinal series of similar paxillee on each side of the 
median row. The series next to the median one have the paxille only very slightly 
elongate transversely, whilst in the outer two rows they are subcircular. None of 
