276 s. goto: 



all. Sometimes a few adclitioual spinelets may be present, external to those 

 above mentioned, and the grouped character becomes then more marked. 

 These spinelets on the actinal surface of the adambidacral plate are covered 

 with membrane like the marginal series, and they have generally a more 

 or less straggling and in-ognlar appearance. 



" The mouth- plates are elongate and narrow, and the united pair form 

 a convex keel actinally. Their arraatm-e consists of a marginal series of 

 small, rather robust, and abruptly tapering spinelets, shorter than the 

 marginal series on the adambulacral plates, about six or seven on the free 

 margin of the plate, although others appear to continue the series up to the 

 outer exti-emit}' of the plate. At the innermost point of each mouth-plate 

 is one elongate, flattened and round-tipped mouth-spine, greatly exceeding 

 an}' of the other spines in size, and the pair of spines at each mouth-angle 

 are j)arallel to one another and directed towards the centre of the actino- 

 stome. At first sight these enlarged spines might be considered as the 

 innermost spines of the marginal series above described, but I am doubtful 

 •whether this is really the case, as there is the singular occmTence in this 

 form of a small group of short spinelets i)i'esent on each plate at a still 

 liigher level than the foremost mouth-spines above mentioned, and this 

 little insignificant group is fui-ther peculiar from the fact that it is not 

 directed towards the centre of the actinostome, but in the direction of a 

 line crossing the ambulacral furrow. If this group of small and abnormally 

 X:)laced spinelets really belongs to the true marginal series it is probable 

 that the i^rominent and enlarged mouth-spine should be reckoned as the 

 foremost of the actinal or superficial series. On the actinal siu'face of each 

 plate is a longitudinal series of eight to twelve rather robust and conically point- 

 ed spinelets, x^arallel to the median suture; and an intermediate series, fewer 

 in number and more widely spaced, between these and the marginal series. 



" Tlie actinal intermediate plates are confined to a very small area in 

 the inten-adial region, but I am unable to say from superficial observi^iion 

 whether their an-angement presents any regularity or not. Each of the 

 plates beai-s two or tlu-ee short, robust, conical tipped spinelets, which liave 

 a more or less marked tendency to form a gi'oup. 



