PORIFERA OF THE L.M.B.C. DISTRICT. 201 
- have acquired both large flagellated chambers and a rigid 
siliceous skeleton. 
Chalina montagu?, Johnston. (Pl. XI., fig. 1.) 
Halichondria montagur, Johnst., Brit. Sponges, p. 99, pl. vi. 
Chalina montagui, Bowerb., B. S., vol. ii., p. 366; vol. iii., pl. Ixviil. 
This species is an addition to the Fauna of our district. 
I found it in a large and rocky tidal pool at Port Erin, 
April, 1890. Johnston records it as ‘‘not uncommon in 
the estuary of Kingsbridge at very low water, adhering to 
stones, and is occasionally taken by the trawl in the open 
sea on the coast of Devon, Conamara, and Dublin Bay.” 
Bowerbank adds to those localities Brighton and Hastings. 
The figure of the sponge, which I give in natural size 
on Pl. XI., was drawn by me from a photograph which 
Dr. Kohn (Chemical Laboratories, University College, 
Liverpool) had kindly taken from the specimen after it 
had been in spirit for some time. The specimen is larger 
than the one figured by Johnston, and differs from it in 
haying shorter and less whip-hke tubular portions. Bower- 
bank’s figure had been taken from a rather poor specimen. 
The colour of the living specimen was straw-yellow. 
The oscula are always placed on the extremity of conical 
elevations, and measure 3 mm. in diameter. 
The spicules are mostly oxea, but a number of styli are 
also present. Both kinds of spicules are slightly curved, 
and measure on an average 0:096 by 0°;008 mm. They are 
imbedded either in ceratose or in the so-called ascending 
fibres. Inside the ceratose the spicules are arranged in 
unispicular rows. The thickness of the ceratose fibre is 
0-007 to 0'036 mm. The diameter of the ceratose meshes 
- varies from 0:05 to 0'l mm. ‘The ascending fibres extend 
throughout the whole mass of the sponge, and give off 
branches in all directions. Their diameter is 0°05 to 0:08 
mm. Inside those ascending fibres the spicules are 
