tubercles commence gradually on the following plates, the second 

 series on the 10 — 11*^ plate, the third on the 11 — 12'^ plate etc. 

 The naked space, parallel to the outer series of tubercles, dis- 

 appears suddenly at the ambitus, where a new series of tubercles 

 occupies its place, as in Astropyga pulvinata; in one of the speci- 

 mens, however, that is not the case, the naked space disappearing 

 here by and by at the ambitus, between the two outer series of 

 large tubercles. The large median interambulacral space is provided 

 with spread miliary tubercles. The ambulacral areas are not raised 

 above the interambulacral ones; there is a primaiy tubercle on every 

 compound plate, whereas in Astropyga a primary tubercle is found 

 only on every other or third ambulacral plate — at all events in 

 A. radiata and pulvinata; how the case is in A. denudata de 

 Meijere does not appear from the description. The uppermost one 

 of the primary ambulacral tubercles is found on about the tenth 

 plate from above. 



The actinal side is very different from Astropyga and, indeed, 

 from all other Diadematids. The large tubercles (there are 12 series 

 in the interambulacral areas, arranged parallel to the median line 

 of the area, as in A. pulvinata) only reach just below the ambitus; 

 then they suddenly diminish very much in size, and from here 

 the whole actinal side is covered by a very close and 

 fine, uniform granulation, through which the limits of 

 tlie plates cannot be traced. In the outer part of this granulation 

 there are, in both areas, indications of an arrangement of the 

 tubercles in longitudinal series, in continuation of the series of 

 large tubercles at the ambitus, but this arrangement is soon lost in 

 the uniform granulation which covers both ambulacral and inter- 

 ambulacral areas. At the edge of the peristome the test is bent 

 strongly inwards, the ambulacral areas being somewhat sunken 

 below the interambulacral ones. In the granulated part of the 

 ambulacral areas the pores are very small, scarcely half so large 

 as those at the ambitus and on the abactinal side (towards the apical 

 system they are much larger). In the outer part of the granulated 



