DENDY—REPORT ON THE CALCAREOUS SPONGES 25 
Genus Leucitia Haeckel (emend.). 
Canal system leuconoid or sylleibid. Skeleton of chamber layer typically composed 
of the centripetally and centrifugally directed apical rays of subdermal and subgastral 
quadriradiates, but subgastral sagittal triradiates and confused chamber layer quadri- 
radiates may be present, while the subgastral quadriradiates may be absent. 
Section B. 
With large oxea or trichoxea, but no microxea. 
13. Leucilla proteus n. sp. 
(Plate 2, fig. 7; Plate 5, fig. 5). 
There are several very small specimens of a Leucilla, attached to an Avicula shell in 
company with a number of other small organisms, for which it seems necessary to propose 
a new specific name. 
R. N. cvr. 1, B (Plate 2, fig. 7) may be taken as typical. The sponge is more or 
less cylindrical in form, with a single vent at the free extremity. The length of the 
specimen selected was about 7 mm. and the diameter 2°5:mm. The colour in spirit was 
white. 
The wall of the sponge, surrounding the central gastral cavity, is rather thin. The 
canal system is sylleibid, almost if not quite syconoid towards the osculum, where the 
flagellate chambers are thimble-shaped and more or less radially arranged. 
The dermal skeleton consists mainly of the facial rays of large quadriradiates, with a 
marked tendency to become sagittal, especially towards the osculum, and then also to be 
oriented in the usual manner, with the unpaired ray pointing aborally. 
The skeleton of the chamber layer consists mainly of the strong apical rays of these 
quadriradiates, which commonly extend right through it and even project into the 
gastral cavity. The comparatively slender basal rays of usually much less strongly 
developed subgastral sagittal triradiates traverse the chamber layer in the opposite 
direction. In one specimen at any rate there are irregularly scattered large radiates in 
the older parts of the chamber layer. (In the same specimen I have also observed 
numerous slender triradiates lying tangentially amongst the dermal quadriradiates. 
I am inclined to regard this specimen as more nearly adult than the others; it is also 
larger.) 
The gastral skeleton is rather feebly developed, consisting of slender, tangentially 
placed triradiates and quadriradiates, and of the oral rays of the subgastral sagittal 
triradiates. Smaller quadriradiates may occur in the walls of the exhalant canals, towards 
the gastral surface. 
Tn some specimens, if not in all, there is a very feebly developed oscular fringe of 
minute, slender oxea, and a few hair-like oxea may also occur, projecting here and there 
from the dermal surface. 
The spicules may be described under the following heads :— 
SECOND SERIES—ZOOLOGY, VOL. XVI. 4 
