658 s. GOTO : 



marginals arc liardly different in appearance from the adjacent 

 dorsal plates. 



The madreporite is very small and can hardly be seen with 

 the naked eye. In the single specimen before me (R=22 mm.) 

 it lies abont 2 mm. from the centre of the disk, which is marked by 

 a conical prominence. 



The adamhulacral armature consists of a single series of ten 

 or eleven slender delicate spines arranged in a deep horse-shoe 

 shape, four or five of them usually facing the ambulacral furrow 

 and being longer than the others, which are more or less turned 

 away from the furrow. The latter spines are sometimes disposed in 

 such a way as to simulate a second outer row of adamhulacral 

 spines, but close examination shows the horse-shoe arrangement to 

 be the true one. The spines are easily flexible and do not offer 

 any perceptible resistance when touched with a metal point. Each 

 mouth-plate bears on its free margin a regular row of seven or 

 eight spines which gradually increase in size towards the mouth, 

 and of which the last two or tln-eo at the central end are parti- 

 cularly stouter ; they are less flexible than the adamhulacral spines. 

 On the actinal ridge of each mouth-plate there is a somewhat 

 irregular row of spines nearly equal in size to those of the furrow 

 series of the mouth-plate, in close apposition with those of the 

 fellow plate, so as to form a single group. The two series of 

 a plate are separated by a distinct space. 



The adamhulacral plates are foUowed by a series of ventro- 

 lateral plates, wliich are distinctly smaller than the other ventro- 

 laterals and bear very short pointed spines, varying fi^om two to seven 

 on each plate. All the remaining ventrolaterals are similar and 

 only decrease in size towards the margin of the body. The larger 



