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 papillse, scarcely distinguishable 

 from the mihary 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 papillae 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 pedicellarise, 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 paxillse 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 paxillse, slightly larger than the rest, and with their transverse 

 diameter a little greater than the longitudinal. On reaching the base of the ray these 

 paxillse 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 paxillse on each side of the 

 median row. The series next to the median one have the paxillse only very slightly 

 elongate transversely, whilst in the outer two rows they are subcircular. None of 



