322 MARINE BIOLOGY OF THE SUDANESE RED SHA. 
a horny lamellibranch shell (? Avicula), and from this mass other branches 
arise. 
The whole specimen stands 160 mm. high from base to summit; the 
branches vary from 10 mm. to 20 mm. in diameter, and the lobes are about 
20 mm. in thickness at their thickest point. 
The oscula are fairly numerous and are scattered irregularly over the 
whole surface of the sponge. They are not of great size, averaging 3 mm. 
in diameter. The pores are very numerous, of comparatively large size, and 
are scattered thickly over the whole of the dermal membrane. 
The colour in spirit is dark brown. 
The texture of the sponge is firm and resistant, but easily compressible. 
The skeleton consists of an irregular network of spicular fibre, the spicules 
of which are cemented together by spongin. As a rule, a series of radial 
primary fibres can be distinguished, but in some parts of the sponge no 
distinction can be drawn between the primary and secondary fibres. The 
secondary fibres uniting the primary fibres form a very irregular reticulation, 
and possess no definite arrangement whatever. The mesh is very variable in 
size, but on the average is between 0°5 mm. and 0°6 mm. in diameter. The 
meshes are quite irregular in shape. 
The primary fibres possess sometimes as many as 10 rows of spicules, and 
usually 7 or 8 rows. In the secondary fibres the spicules rarely lie more 
than 2-3-serial, though fibres intermediate between primary and secondary 
may be found in some parts with 5-8 rows of spicules. The spongin coating 
the spicules is somewhat scanty and only just shows outside the fibres. The 
dermal membrane is supported by an extremely fine fibre-network, in which 
the spicules rarely lie more than 2-serial, and the meshes of which are 
very fine. 
Outside these fibres a very few oxea can be found lying in the sponge 
substance without any orientation. They are exactly similar to those of the 
fibres. 
The spicules are almost wholly diactinal, but a very few styles may be 
found occasionally intermingled with the oxea. They are certainly only 
accidental malformations of the typical spicules, and not true styles. 
The oxea are fairly large, reaching 0:16 mm. in length by 0-004 mm. in 
diameter. These measurements are slightly larger than those given by 
Dendy for this species in the type specimens from the West Indies, but 
otherwise the two specimens are extremely similar. Dendy’s measurements 
are: length 0°126 mm., diameter 0:003 mm. 
Locality. No definite locality is given for this sponge, but merely “ Sponge 
Trials 1.” 
Distribution. Red Sea, West Indies. 
