14 
TH. MORTENSEN, 
(Schwed. Südpolar-Exp. 
there is at the lower edge of each plate a much smaller tubercle, the whole area 
thus carrying four vertical series of tubercles. According to AGASSIZ (Revision of 
Echini p. 396) there are, besides the primary series, »two irregular vertical rows on 
each side of the median furrow, with a few miliaries scattered irregularly between 
the secondary tubercles towards the poriferous zone». Even in the largest specimens 
examined by me (26 mm. in diameter) I find only one secondary tubercle on each 
plate; the second of these small tubercles is thus evidently found only in still larger 
specimens (comp, below, the specimens from Altata?). — The median furrow is nar- 
row, but mostly quite distinct. The pores are described in the »Revision» as »ad- 
joining; ridge separating pairs of pores prominent». This is quite correct, and it 
need only be added that there is a distinct depression all round each pair (Fig. 4). 
(The difference in the shape of the pores between this species and E. nutrix has 
been emphasized in the Report on the Echinoidea of the German Southpolar-Expe- 
dition; Fig. 4 to compare with Taf. X Fig. 7 of the latter 
work.) — In the larger specimens there are 5 — 6 ambu- 
lacral plates to each interambulacral plate, at the ambitus. 
The interambulacra are especially remarkable by 
the broad, deep, sharply cut, median furrow, which I 
find to be distinct in all the specimens before me (PI. 
IV Fig. 4). (Regarding the quite young specimens 
comp, below.) The areoles are rather deep, only those 
nearest the peristome confluent. The circle of tubercles 
surrounding the areoles rather prominent; outside this 
circle a few smaller tubercles occur at the outer edge 
of the plates and some more adjoining the median 
furrow. These tubercles are considerably smaller than 
those of the edge of the areoles. 
The apical system (PI. IV Figs. 5—6, 9— 10; PI. XIV Fig. 6) is comparatively 
small, ca. 41—44 % of the horizontal diameter of the test. The ocular plates are in 
larger specimens generally all in broad contact with the anal system. DöDERLEINS 
Fig. 4. Ambulacral pores of Austro- 
cidaris canaliculata. 42 / 1. 
statement (loc. cit.) that he finds »bei einem ziemlich grossen Exemplar ... das 
Analfeld vollständig eingeschlossen von den Genitalplatten», evidently refers to the 
specimen of E. nutrix and thus has no bearing on any variability in this character 
in canaliculata. Further, when AGASSIZ says in »Revision of Echini» p. 396: »Genital 
plates in contact», which cannot mean anything but that the oculars are excluded 
from the anal area, I would suggest that »genital» is a lapsus calami for »ocular». - 
The ocular plates are distinctly broader than high, lozenge-shaped, a somewhat un- 
common form; the inner angle is generally cut off to some extent, the more so the 
older the specimen; the ocular pore is situated in the outer angle, not near the 
