14 
AUSTRALASIAN ANTARCTIC EXPEDITION. 
Spicules :— 
(1) Regular triradiates of the chamber layer and gastral cortex (fig. 10a). Equi¬ 
angular and equiradiate, with long, slender rays all lying approximately in 
the same plane. Rays nearly cylindrical and rather abruptly pointed, often 
very slightly crooked, or irregular in thickness; measuring about 0-2 by 0-005 mm. 
(2) Quadriradiates of the gastral cortex (fig. lOd); very similar to the triradiates 
just described, but with a feebly developed apical ray, usually represented 
by nothing more than a small knob. 
(3) Regular triradiates of the dermal cortex (figs. 106, 10c), with the rays bent in 
such a way that the centre of the spicule is lifted up considerably above the 
plane in which the three apices lie. Rays conical, fairly gradually but not 
very sharply pointed, stouter than those of the radiates above described; 
measuring, say, about 0-12 mm. in length by 0-012 mm. in diameter at the 
base, but, of course, variable. In boiled-out preparations, these spicules are 
usually found resting on two of the rays, with the third tilted up and 
commonly broken off short, as shown in fig. 10c. 
The canal system is “ sylleibid in type, the flagellate chambers being large 
and irregularly sac-shaped, measuring about 0-26 mm. in maximum diameter. The 
inhalant pores are thickly scattered over the outer surface and lead through the dermal 
cortex into the large, irregular, inhalant lacunae. Similar, but larger, exhalant lacunae, 
formed by the union of smaller ones, open on the gastral surface. 
The specimen is badly preserved histologically and I have not been able to deter¬ 
mine the position of the nuclei in the collared cells. 
As regards canal system, this species resembles Leucandra austr aliens is, as figured 
by myself (1893), but it differs in the absence of oxea, as well as in other respects. Of 
previously fully described species the one which, perhaps, comes nearest to it seems 
to be Leucandra telum, which Lendenfeld (1891) referred to his genus Polejna, charac¬ 
terized by the “ Sylleibid ” canal system combined with the absence of oxea; but the 
two differ widely in external form, as well as in skeletal features. 
Three Antarctic species described by Jenkin (1908), viz. —Leucandra frigida 
L. brumalis, and L. gelatinosa, belong to the same section of the genus, but their canal 
system is very imperfectly known, and in any case they seem to be quite distinct from 
X. mawsoni. 
Altogether Leucandra mawsoni appears to be a very well characterised species, 
easily recognised by its external form and by the peculiar, almost tripod-like dermal 
triradiates. 
I have much pleasure in dedicating this species to the distinguished leader of 
the Expedition, Sir Douglas Mawson. 
Register No., Locality, &c., Ill, Station VII (lat. S. 65° 92', long. E. 92° 10'), 
60 fathoms, 21-1-14. 
