26 PERCY SLADEN TRUST EXPEDITION 
(1) Quadriradiates of the dermal surface (Plate 5, fig. 5 a, b); with all four rays 
strongly developed, stout and fairly sharply pointed ; facial rays lying tangentially to the 
surface, commonly more or less sagittal; apical ray directed centripetally through the 
chamber layer, either longer or shorter than facial rays; size variable, facial rays 
measuring say about 0°39 by 0°035 mm. 
(2) Quadriradiates of the gastral surface (Plate 5, fig. 5 d); much smaller than (1), 
with slender, sharp-pointed facial rays and short, sharp-pointed apical ray projecting into 
the gastral cavity ; facial rays measuring about 0°16 by 0:015 mm. These spicules become 
strongly sagittal towards the oscular margin, with the recurved oral rays stouter than the 
basal ray. 
(3) Triradiates of the gastral surface (Plate 5, fig. 5); similar in all respects 
to (2), except for the absence of the apical ray, and like them becoming strongly sagittal 
at the oscular margin. 
(4) Quadriradiates of the exhalant canals; much smaller than the gastral quadri- 
radiates and with proportionally longer apical rays. 
(5) Subgastral sagittal triradiates (Plate 5, fig. 5 c); with the two oral rays widely 
extended in a line with one another beneath the gastral surface and the basal ray directed 
centrifugally through the chamber layer. All rays gradually and sharply pointed. Size 
very variable, averaging perhaps about 0°18 by 0°02 mm. for the oral rays and 0°33 by 
0-02 mm. for the basal ray. 
(6) Oxea; these occur chiefly in the oscular margin, where they form a very feebly 
developed fringe. They are very slender, not very long, and very sharply pointed at each 
end; almost hair-like, but sometimes with a distinct swelling at some distance from the 
finely drawn out distal extremity, length say about 0125 mm. These spicules seem to be 
intermediate between microxea and trichoxea. 
This species is evidently very closely related to Leucilla australiensis (Carter)*, and 
it may even prove to be specifically indistinguishable. The following differences may, 
however, be indicated. 
(1) The external form is cylindrical rather than ovoid. 
(2) The sponge wall is thinner. 
(3) The skeleton of the chamber layer is almost entirely composed of the apical rays 
of the subdermal quadriradiates and the basal rays of the subgastral triradiates, whereas in 
L. australiensis there is a well developed skeleton of confused radiates in the chamber layer. 
(4) Oxea are present. These may or may not be constant and it is possible that 
they may also occur in L. australiensis, though they have never been observed in that 
species except in one doubtful case where a very few were found (possibly accidental). 
It is highly probable that all the specimens of L. proteus obtained by the “ Sealark ” 
are young and that some of the apparent differences between them and L. australiensis 
may disappear in later life. 
Register Nos., Localities, dc. cvi. 1, A, B, C, D, &c., Amirante, 13.10.05, E. 16, 
39 fathoms. 
* 11886, p. 133.] 
