364 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
The mesogleea is abundant, and is filled with cells, which are mostly stellate, 
though some appear circular. The mesoglea is not granular, and there are 
no fibres or pigment-cells. 
Locality. Not stated. 
Distribution. Red Sea. 
SPONGELIA DELICATULA, N. sp. 
The single specimen obtained of this species consists of a group of small 
flat branches, which are irregularly lobed or slightly branched, and usually 
more or less strap-shaped. They are thinnest at the centre of the branch, 
and thicken out at the sides into a ridge. The height of the branches is 
55 mm., their width anything from 5 mm. to 20 mm. and their thickness 
from 1 mm. to 5 mm. 
The surface is covered with small conuli, regularly arranged over the whole 
sponge surface, and each with a spongin-fibre protruding from the centre. 
These conuli do not exceed 0°25 mm. in height, and are about 1:0 mm. to 
1-5 mm. apart. 
Oscula and pores were not distinguishable. 
The colour of the sponge is horn-grey in spirit. 
The texture of the sponge is firm, but the sponge is not rigid, but easily 
bent or twisted out of shape. It immediately regains its shape when 
released. 
Skeleton a rrangement. 
The skeleton consists of an irregular sparse reticulation of spongin-fibre 
which is always filled with sand-grains, and does not present any differen- 
tiation into primary and secondary fibres. The fibres run quite irregularly in 
the sponge, but all end in the conuli on the surface, of which they form the 
support. They measure from 0:08 mm. to 071 mm. in diameter. 
Canal-system and Chambers. 
The whole sponge is highly vacuolated, owing to the great size of the 
inhalant and exhalant canals. Indeed, it may be said that the tissues of the 
sponge merely form a series of trabeculze between the various canals. The 
canals may reach any diameter up to 0°5 mm., while the sarcode between 
them rarely exceeds 0:2 mm. 
The flagellated chambers are not easy to see and are rather scarce; they 
measure 0°06 mm. to 0-08 mm. in diameter ; they are eurypylous and open 
directly into large exhalant canals. The preservation was not sufficiently 
good for any further details of the canal-system to be made out. 
There is a cortex in the form of a narrow dermal band of fibrous tissue, 
