316 THE VOYAGE OF H.M.S. CHALLENGER. 
little towards the bluntly pointed tip; three are usually placed on each facet of the 
angulated margin, and when directed over the furrow their radiation is more or less 
dominated by an apparent separation into two sets, to a certain extent divergent from one 
another. The furrow series has the appearance of being continued along the lateral 
margins of the adambulacral plates (7.e. at right angles to the furrow), in consequence of 
the presence of three or four short papilliform spinelets. These spinelets diminish in size 
as they recede from the furrow margin, and their number decreases as the breadth of the 
plates becomes less as they proceed along the ray. A lineal series of three or four small 
papuliform granules proceeds along the outer end of the plate, parallel to the furrow, and 
thus completes the surrounding of the outer margin. On the area of the plate are one or 
two small spinelets similar to the furrow series, but one is often slightly longer and more 
pointed, and is placed in such a manner between the first spinelets of the lateral series of 
each side of the plate as to appear to form with them a longitudinal series parallel to the 
furrow, and with the small marginal series on the outer end of the plate. On the plates 
close to the mouth-plates additional spinelets are present. 
The actinal interradial areas are small and triangular, with the base slightly curved. 
They are covered with small paxilliform plates which bear short papilliform spinelets, 
marginally placed, with one or more central, but owing to crowding and irregularity they 
often appear more or less like groups and are badly defined. 
The mouth-plates are elongate, suboval, and slightly convex or subtubercular on the 
actinal surface. They are rather closely covered with short papilliform spinelets, the 
number and arrangement of which it is difficult to formulate. There may, however, be 
distinguished (1) a series running parallel to the median suture; (2) a series on the 
opposite angulated margin,—part falling in the furrow, which is more or less crowded as 
it reaches the mouth, and part on the margin adjacent to the adambulacral plate; and 
(3) some intermediate spinelets usually confined to the inner and median part of the area. 
The spinelets are all short and vary very little in size, though they diminish slightly 
on the outer part of the plate: the mouth-plates consequently have a very echinulate 
appearance. 
The abactinal paxillar area is a well-defined pentagon, with slightly curved sides; and 
its general surface does not exhibit any special inflation. Outward from the primary 
radial plate the median radial line is occupied by a longitudinal series of hexagonal 
paxillee which diminish slightly in size and gradually assume a quadrate shape as they 
approach the base of the ray; from this point they are continued along the median line of ' 
the ray as an uninterrupted series of uniform, small, square plates, against which the 
supero-marginal plates on each side of the ray abut. The breadth of these plates at the 
base of the ray is slightly less than 1 mm. Parallel to the median radial series of disk 
paxillee are other longitudinal series of similar paxille, each series showing a slight diminu- 
tion in the size of the paxille as they recede from the median series. These lateral series 
