254 s. GOTO : 



seen from the surface the adambulacral plates are nearly square 

 near the mouth, but they soon become longer than broad to- 

 wards the middle of the arms, and again become as broad as 

 long toward the tip of the arms. At the furrow margin on 

 each plate there is a series of very conspicuous, long spines, 7-9 

 in number, with the central ones longer and those towards the 

 two ends shorter (PI. VIII, fig. 138). These spines are very 

 stout, pointed at the end, angular and flattened transversely to 

 the furrow, so that a cross- section of any one of them w^ould be 

 a regular rectangle. On the actinal surface of the plate there 

 are some very sharply pointed spines with enlarged bases appar- 

 ently without any regular arrangement, some twenty in number. 

 These spines are much shorter and more slender than those of 

 the furrow series. 



Mouth-plates. — These are very large, and when denuded of 

 their spines are seen to be lightly ankylosed together for a short 

 distance at the mouth end. Each plate is comparatively long 

 and narrow, and the outline of its external margin is somewhat 

 like that of a brace (PI. VIII, fig. 137). Along the edge border- 

 ing on the ambulacral furrow there is a conspicuous series of 

 very stout, angular, flattened spines, mostly with truncated 

 ends, ten to a dozen in number (PI. VIII, fig. 136). The spine 

 at the moutli end is stout, but it does not project prominently 

 towards the mouth ; the spines at the farther end of the series 

 is smaller and more pointed in form. The above mentioned 

 furrow series of spines encloses with its fellow an area on the 

 mouth-plates, in which there are usually from a dozen to fifteen 

 sharply pointed spines, considerably smaller than those of the 

 furrow series. They are usually more or less conical in form. 



