Bd. VI: 4) 



THE ECHINOIDEA. 



2 3 



Austrocidaris spinulosa n. sp. 



PL III Figs. 3—5, PL 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. 



9 ■ ■ ■ 



27 



17 



12 



7 



8 



3 



•3 



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 



i-5 



5-5 



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 

 catialiculata it has not the test incurved at the edge of 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 { 9 <M 



tubercles seem to be somewhat less prominent ^f~~> J J ' ST^ ^ ^ ' ^> 



and the part of the ambulacral plate above the / 



pores perhaps somewhat more elevated (PI. XIV / '» : a i t^~r^y^\\ ^)~~ / \ ' t> l"'^j 

 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 ji^y' 

 coronal plates seems to be smaller than in cana- 



liculata - 7 in the larger of the specimens in Flg ' 6 ' Apical system of Austrocidaris 

 ' 0 r spinulosa. 45 /«. 



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 



