R. w. H. ROW—REPORT ON THE SPONGES : NON-CALCAREA. 293 
Family STELLETTID @. 
Astrotetraxonida with long shafted trieenes, without calthrops and without 
sterrasters. 
PILocHRora PARVA,n. sp. (PI. 35. fig. 3, Pl. 36. fig. 6 ; text-fig. 1.) 
The only specimen of this new species in the collection is a small, irregular 
but complete specimen, without any indication of attachment, and measuring 
about 20 mm. by 15 mm. 
Several prominences and protuberances occur on the sponge, and it is 
quite impossible to distinguish an upper or lower surface. Two com- 
paratively large oscula occur on the specimen, one near each end of the 
sponge, and each is somewhat oval in shape. The larger measures 1:2 mm. 
in its longest diameter and the smaller measures 0°83 mm. The pores are 
extremely numerous and are thickly distributed over the whole surface. 
There are no special pore-areas, but the pores frequently lie at the bottom of 
slight depressions on the sponge surface. 
The texture is hard and brittle, and the colour in spirit white. 
The surface of the sponge is perfectly smooth, there being no projecting 
spicules whatever, though slight irregularities and pits occur over the 
surface. . 
The cortex is 1:0 mm. thick, and definitely marked off from the choano- 
some. It contains numerous large subdermal cavities, which are oval in 
shape, with the long axis of the oval lying vertically in the sponge. Between 
these cavities occur fan-like groups of spicules composed almost entirely of 
ortho- and anatrieenes, the heads of which lie immediately below the dermal 
membrane. The rays of these trizenes lie nearly always wholly in the cortex, 
very rarely projecting into the choanosome. 
Immediately below the cortex lie the heads of the triznes of the main 
skeleton, which is radially arranged, but not gathered up into distinct fibres 
or bundles of spicules. Amongst the triznes lie large numbers of oxea. 
Both the cortex and the choanosome are filled with enormous quantities of 
chiasters. 
Spicules. 
A. Megascleres. 
(«) Orthotriznes. (Text-fig. 1, A.) 
The orthotriznes of the cortex are not to be distinguished from those of 
the choanosome. The rhabdome is conical, delicately pointed, and is thickest 
at the head, and quite straight. Its length is from 1-0 mm. to 1:15 mm. and 
the average thickness is 0°023 mm. The cladi are fairly long, curved from the 
base onwards, and frequently recurved back again to the horizontal They 
reach a length of 0:2 mm. in the largest specimens. 
