324 THE VOYAGE OF H.M.S. CHALLENGER. 



The radial plates internal to the large tubercle generally bear a small tubercle ; and no 

 other plates in the median radial series are thus armed. Many of the plates in the two 

 longitudinal series on each side of the median radial series bear similar and more or less 

 conical tubercles. These tubercles form more or less definite lines, which gradually con- 

 verge towards the centre and mark out a lanceolate ficnire in each radial area. 



The supero-marginal plates, which are twenty-two in number, counting from the 

 median interradial line to the extremity, form a broad well-defined border. Each plate is 

 distinctly and prominently tumid, and all are covered with the same uniform granulation 

 and skin as that already described on the abactinal plates. Three or four of the supero- 

 marginal plates on each side of the median interradial line bear a single small and more or 

 less conical tubercle on the convexity between the abactinal and lateral areas ; and these 

 tubercles are much more conspicuous and relatively larger in small examples. The terminal 

 plate is small, rounded, subovate, and widest posteriorly. 



The infero-marginal plates correspond to the superior series and are similarly tumid, but 

 to a less degree. They are covered with a similar granulation and membrane. Each plate, 

 except those near the end of the ray, bears three large, robust, slightly flattened lateral 

 spines, which are disposed in an oblique line passing from the upper margin to the aboral 

 margin. The upper or outermost spine is the largest, and measures 8 or 9 mm. ; the second 

 is rather smaller ; and the third or innermost is not more than one half the size of the 

 largest, and may be less. All are robust at the base and taper to the extremity ; the two 

 largest are usually obtuse at the tip, and the innermost is pointed. The direction of these 

 spines is upward and outward, and they have an appressed posture, as much as the tumidity 

 of the plate will allow. At the end of the ray only two lateral spines are present, and 

 these are small. There are also only two spines on the first two plates in the inter- 

 brachial arc. 



The adambulacral plates are small and their armature consists of : — (1.) A furrow series of 

 seven or eight short lamelliform spinelets, bluntly rounded at the tip ; these spinelets stand 

 more or less palisade-like, and their greatest surface is at right angles to the furrow. (2.) 

 On the actinal surface of the plate are two large, equal-sized, flattened, and somewhat 

 gouge-shaped or elongately spatuliform spinelets, which stand side by side, and occupy the 

 whole breadth of the plate, forming a line parallel to the furrow series. The largest 

 measure nearly 4 mm. in length. On the outer part of the ray (about the last third) only 

 one actinal spine is present. Between the furrow series and the actinal spines at the adoral 

 edge of the plate is a small two-valved pedicellaria. The outer part of the plate external 

 to the actinal spines is covered with a small uniform granulation imbedded in membrane 

 similar to, and continuous with, that which covers the actinal intermediate plates, and in 

 fact all the surface of this species. 



The mouth-plates are small, slightly prominent actinally, forming a low arched keel, 

 and their surface is covered with a granulation similar to that above described. Their 



