147 
the plate opposite the suture between each two interambulacral 
plates generally is higher than the rest of them and carries a tub- 
ercle, sometimes nearly as large as the primary one, at the outer 
edge, above the pores. There is only a very narrow ridge between 
the pores of each pair, hardly showing any elevation. Figures of 
the naked test have been given by Clark (The Cidaridæ, PI. X. 
3—4), to which may be referred. 
The apical system nearly as large as the peristome. The ocul- 
ars are all exsert. The outline of the plates may be seen from 
textfig. 1. The genital pores of the females are very large, situ- 
ated at the outer corner of the genital plates; in the males they 
are much smaller and are situated a good distance from the edge. 
In both sexes they are covered by the surrounding spines, which 
stand much doser here than on the inner part of the plate. — 
The large female genital pores indicate that the eggs are large 
and yolky,which leads to the suggestion that this species may 
perhaps protect its brood as do so many other Cidarids of the ant- 
arctic and subantarctic regions. The peristome is almost without 
spines in the outer part, the plates being there rather high, and 
the ambulacral pores accordingly fairly distant. In the inner part 
the plates are very much lower, and the pores stand very close, 
the two series of each ambulacrum forming together a distinet arch 
at the mouth-edge. These inner plates are closely covered with spines. 
The colour of the naked test is distinetly greenish on the aboral 
side. 
The radioles are rather short, generally only Vs— 3 /T of the 
diameter of the test; only in one of the specimens in hånd they 
slightly exceed the diameter of test. The oral radioles are only 
little specialized, with slightly serrate edges; those at the ambitus 
generally have a pair of coarse blunt thorns at the base; they are 
slightly tapering, with somewhate serrate longitudinal ridges. The 
upper radioles are quite short, widened at the point into a flat or 
slightly concave disk, sometimes only small, sometimes very large 
(PI. VI, Figs. 1—2). Intact radioles, not worn or covered by for- 
eign organisms (as they generally are) are found to have, espec- 
‘) I have opened one of the alcoholic specimens and thus can assert 
that the eggs are really large and yolky; the exact size cannot begiven, 
the preservation not being very satisfactory. 
to* 
