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mouth end one or two pointed spines notably larger than the 

 rest, and 4-0 pointed spines of unequal sizes on the furrow 

 border (PI. VIT, fig. 115 ; PL VIII, fig. 122). On the border of 

 the plate facing the first adambulacral plate there is a row of 

 four or five inconspicuous stunted spines nearly covered over by 

 the humid membrane of the body surface, while on the actinal 

 surface of the plate there may be 1-8 short spinelets of unequal 

 sizes, of which the one next the large oral spine may be sub- 

 equal to the latter. In some specimens the inner intermediate 

 plate at the abcentral end of each pair of mouth-plates comes 

 out distinctly to view and in such cases its abcentral border may 

 be armed with six to eight indistinct spinelets mostly covered 

 over by the superficial membrane. 



Ventrolaterals. — The ventrolateral plates are very well 

 developed and appear to be subject to a great deal of variation. 

 They are arranged in obliquely transverse rows parallel to the 

 inter radial line and are divided into groups covered over by the 

 same humid membrane as that of the marginals and the ad- 

 ambulacral plates ; each group is separated from the next by a 

 deep furrow continuous with the fasciolar grooves of the marginals. 

 In most cases there are two transverse rows of ventrolateral plates 

 corresponding to each marginal, but cccasionally one or more plates 

 may be intercalated between the two rows of a single group (PL 

 VIII, fig. 122). In larger specimens the ventrolateral plates extend 

 outwards as far as the sixth marginal, but in smaller specimens 

 they may terminate with the fourth. Again, the number of plates 

 that form a single transverse row varies a good deal ; e.g. in a 

 specimen with ri = 27mm. there w^ere eight plate in a single row 

 next the interradial fine, while in another w^ith E = 23mm. there 



