Bd. VI: 4) 
THE ECHINOIDEA. 
5 
near the peristome and near the apical system in larger specimens. — The pores 
are rather large, very close together, separated only by a very thin wall, which is 
even generally interrupted in the middle, the pores thus becoming confluent (Fig. i). 
The poriferous part of the ambulacral plates scarcely so broad as the non-poriferous 
part; it is not so distinctly sunken. — 9 — 10 ambulacral plates correspond to each 
interambulacral plate at the upper part of the test. 
Interambulacra. The areoles are rather deep, all confluent except the three upper 
ones, which latter alone are round, all the lower ones being oval. The median space 
rather broad, closely covered by uniformly sized secondary tubercles, with numerous 
small miliary tubercles between them. There is thus no naked space along the 
scarcely depressed, median line. The beginning (at the median line) of the hori- 
zontal sutures is generally marked by a more or less distinct depression. The tu- 
bercles around the areoles are not larger than the 
ocular plates are all excluded from the anal system; — 
they are rather deeply notched in the outer edge, Fig- i- Ambulacral pores of Ctenocidaris 
,. , speciosa. 2 %- 
which is otherwise sometimes more angular, some- 
times more rounded (PI. IV Fig. 2, PI. XIII Fig. 2). The pore is surrounded by 
a distinct elevation, like a ring-wall. They are covered by rather numerous small 
tubercles, except a more or less broad margin along the inner and outer edges, which 
remains bare. The genital plates are considerably broader than long, like the oculars 
covered by secondary tubercles leaving the margin bare. The female genital openings 
are very large, ca. 2 mm in diameter, close to the outer edge or even breaking 
through the edge of the plate (Plate XIII Fig. 2). The male genital openings are 
very small and remote from the edge (PI. IV P'ig. 2). The anal area is covered by 
an outer circle of rather large plates, inside which comes another circle of smaller 
plates; the middle part is covered by quite small plates, which become more or less 
elongate towards the anal opening. The whole anal system is, in the larger speci- 
mens, generally much elevated; the elevation begins already outside the anal system, 
the genital plates being more or less raised in their inner part. 
The peristome is somewhat smaller than the apical system, ca. 35 — 42 / of the 
h. d., but likewise comparatively a little larger in young specimens. The ambulacral 
plates of the peristome are numerous, ca. 12 in larger specimens; towards the outer 
other secondary tubercles. Also the rather narrow 
margin outside the areoles is closely covered by 
secondary tubercles. 
The apical system is somewhat less than half 
the horizontal diameter, ca. 40 — 47 /] in the quite 
young specimens it is comparatively a little larger, 
as seen by the measurements given above. The 
