330 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
upright, rather thick lamella, growing from a small circular base. The 
attachment of the sponge is absent, and a portion of the sponge has been lost 
with it. The whole specimen is 40 mm. high, 30 mm. wide, and 8 mm. to 
10 mm. thick. 
The external surface, where visible, is almost exactly like that of 
Acanthoxifer, Dendy (11) ; the whole surface of the sponge is lined by pore- 
grooves, which divide up the surface into a number of polygonal or rounded 
areas, which measure from 3 mm. to 6 mm. in diameter. The pore-grooves 
are usually about 1:5 mm. wide. Hach of the polygonal areas marked out 
by the pore-grooves is somewhat higher in the centre than at the edge, so that 
it has the form of a very low rounded eminence, with a perfectly smooth 
surface. 
The pore-areas possess a special skeleton, but it is very slightly different 
from that of the general dermal skeleton. On the outside it is marked by 
the fact that the brushes of spicules project somewhat further from the surface 
than they do elsewhere. The pore-groove thus presents the appearance of a 
densely, but minutely, hispid ridge, raised very slightly above the immediate 
surrounding surface. 
The colour of the sponge is a very slightly yellowish white, a colour 
probably due to the fact that it was placed in the same bottle as some deep 
yellow specimens, and the spirit in which the sponges were preserved is 
coloured a very deep yellow. Since there is no spongin in the specimen, 
and the surface is densely covered with spicules, the probability is that in life 
the sponge was a brilliant white. 
The texture of the sponge is firm, almost hard, and the sponge can 
only be cut with difficulty. 
Skeleton arrangement. 
The main skeleton consists of a very dense mass of oxea, felted together 
without any orientation save at the surface. The whole sponge contains 
immense numbers of oxea throughout, almost filling the entire specimen. At 
the surface there are a very large number of small brushes of similar oxea, 
packed closely together, and forming a cortical skeleton. 
Over the polygonal areas these brushes of spicules do neither attain a large 
size nor project much from the surface; but in the pore-grooves they are 
very large, sometimes containing 30 or 40 spicules, and they project con- 
siderably from the surface. In the size and shape of the spicules, however, 
they do not differ either from the other dermal spicular brushes or from the 
main skeleton. 
