31G 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 (i.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 

 papilliform 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 (l) 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 

 paxillse 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 

 paxilke are other longitudinal series of similar paxillae, each series showing a slight diminu- 

 tion in the size of the paxillae as they recede from the median series. These lateral series 



