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former. Each inferoraarginal plate presents either a more or less 

 convex or a broadly wedge-shaped border towards the ventro- 

 lateral areas. The granulations and the pedicellariœ are exactly 

 similar to those of the superomarginals. 



Aclamhidacrals. — In the disk tlio adambulacral plates are 

 more elevated than tlie ventrolaterals,'^ but in the arms the two 

 are on a level. Along the greater part of the furrow each 

 adambulacral plate is only very slightly broader than long, so 

 that it is very nearly square in form ; the outer border is, how- 

 ever, frequently either convex or wedge-shaped. The adam- 

 bulacral armature is subject to some variation. On the furrow 

 border is a series of three or four stout, flattened spines, of 

 which the central one or ones are larger than the others (PJ. XII, 

 fig. 183). Occasionally, however, there are three large and two 

 very small spines. On many of tlie plates this furrow series leaves 

 the proximal part of the furrow border of the plate free, 

 evidently in relation to the pedicellaria to be mentioned in con- 

 nection with the second row. This consists of one or two thick 

 conical spines and a pedicellaria at the proximal end. The spines 

 may be as long as those of the furrow series, but are usually 

 shorter and thicker. When there arc two spines they may be very 

 unequal in size. The pedicellaria, which is valvate in form, is 

 mostly placed with its length slightly oblique to the ambulacral 

 furrow, and is inequivalve, with the smaller valve facing the 

 furrow (PI. XII, fig. 190). Next follows a row of two to four 

 large, conico- elliptical granules, and separated from it by a space 

 is the last series of smaller granules placed along the outer mar- 

 gin of the plate, except where this is occupied by the other rows. 



1) This condition may. ho\;ever. be altered in inflated specimens. 



