Bd. VI: 4) 
THE ECHINOIDEA. 
23 
Austrocidaris spinulosa n. sp. 
PI. III Figs. 3 — 5, PI. XIV Figs. 3 — 5, 12 — 15. 
Dia- 
meter. 
Height. 
Apical 
system. 
Anal 
system. 
Peri- 
stome. 
Width of 
Number of plates. 
Radioles. 
Ambulacra. 
Inter- 
ambulacra. 
Ambulacra. 
Inter- 
ambulacra. 
mm. 
mm. 
mm. 
mm. 
mm. 
mm. 
mm. 
mm. 
9 ■■ ■ 
27 
1 7 
12 
7 
8 
3 
o 
35-36 
7 
49 
h 
7-5 
6.3 
4 
7 
1.8 
7 
19 — 20 
5-6 
28 
1 1 
6 
5 
3 
6 
ï -5 
5 -S 
15—16 
5-6 
20 
This species, upon the whole, resembles canaliculata very much in the structure 
of the test. The height of the test and the relative size of the peristome and the apical 
system are in the larger specimen comparatively greater than in canaliculata at a 
corresponding size; but it is, of course, impossible to know, from the slight material 
available (only the three specimens whose measurements are given above), whether 
this is a constant feature. In the smaller specimens there is no distinct difference 
in these respects from specimens of canaliculata of a corresponding size. Like 
canaliculata it has not the test incurved at the edge ot the peristome; on the other 
hand, it differs conspicuously from canaliculata in having the apical system flat, not 
sunken, and since the larger specimen is a female, evidently quite ripe and nearly 
fullgrown, there is every evidence that this is a specific feature. 
The ambulacra do not present any distinct 
difference from canaliculata , only the primary 
tubercles seem to be somewhat less prominent 
and the part of the ambulacral plate above the 
pores perhaps somewhat more elevated (PI. XIV 
Fig. 3). The interambulacra are upon the whole 
as in canaliculata, though the areoles are, per- 
haps, a little larger than in that species, and 
the part of the plates between the areoles and 
the deep median line accordingly a little nar- 
rower. On the other hand, the number of the 
coronal plates seems to be smaller than in cana- 
liculata — 7 in the larger of the specimens in 
hand against 8 in a specimen of 26 mm. dia- 
meter of canaliculata. This makes a conspicuous difference, the plates thus being 
comparatively higher in spinulosa; it is in accordance with this fact that the areoles 
on the actinal side are not so close together, at most I — 2 being confluent, whereas 
Fig. 6. Apical system of Austrocidaris 
spinulosa. 4S /i. 
