Bd. VI: 4) 
THE ECHINOIDEA. 
21 
are of considerable interest, especially the larger one, so that I feel justified in giv- 
ing a short description of them, noticing the points of difference from canaliculata. 
The measurements are as follows: 
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 • • • 
42 
22 
* 5-5 
1 1 
16 
4-5 
20 
42-43 
OO 
1 
27 
c? • • • 
20 
II 
8.5 
5-5 
9 
2.4 
10 
CO 
1 
O 
ro 
00 
1 
26.5 
The younger specimen differs from an equally sized specimen from South Ame- 
rica in the genital plates having a less prominent outer angle (PI. XIV Fig. 6). On 
the peristome the interambulacral spaces are somewhat narrower within, the inter- 
ambulacral plates thus scarcely reaching to the mouth-opening. Otherwise I do not 
see any differences from the typical form. 
The larger specimen differs considerably more from the typical form. The 
apical system is especially interesting (PI. XIV Fig. io). The genital and ocular 
plates have been greatly reduced, the former even partly split up into small irregular 
plates, so that it can scarcely be said with certainty which of them represent the gen- 
ital plates; only the madreporite has almost kept its original size. In accordance with 
this reduction of the genital plates the anal system has greatly increased in size; on 
account of the small size of the numerous anal plates it is somewhat movable, much 
as in an Echinus. The whole apical system to some degree recalls that of the 
Echinothurids (especially on account of the great reduction of the genital plates). 
One is also reminded of the apical system of » Stephanocidaris », the »echinoid» cha- 
racter of whose anal system is so persistently emphasized by AGASSIZ and CLARK. 
The small upper interambulacral plates are closely covered with secondary tu- 
bercles round the rather small areoles, whereas otherwise the upper plates are ge- 
nerally more or less naked. This means, evidently, that this specimen has reached 
its full size, and these upper plates are not increasing in size any more; likewise no 
small, just beginning, plates are found at the outer sides of the genital plates, as are 
elsewhere generally found. — The Fig. 7 PI. II of the »Challenger» Echinoidea pro- 
bably represents a similar stage. — The upper radioles are also fully formed, though 
considerably smaller than those at the ambitus. (Unfortunately I did not observe 
the quite uppermost ones before denuding the apical part; evidently they have not 
been longer than the secondary spines.) 
hese species — the more so, as the captain who brought the collection from Altata to Salmtn had also 
dredged on the coast of Patagonia in depths of 40 — 50 fathoms. After this I do not doubt that these 
wo specimens are really from South America, not from Altata. 
