2 ' 
tubercles commence gradually on the following plates, the second 
series on the 10—ll th plate, tlie third on the 11 — I2 th plate etc. 
The naked space, parallel to the outer series of tubercles, dis- 
appears suddenly at the ambitus, vvliere a new series of tubercles 
occupies its place, as in Astropyga pulvincita ; 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 primary tubercle on every 
compound plate, wliereas 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, inde ed, 
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 vvhich the limits of 
the 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 hent 
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 ahactinal side (towards the apical 
system they are much larger). In the outer part of the granulated 
