R. W. H. ROW—REPORT ON THE SPONGES : NON-CALCAREA. 367 
almost identical size, though one of them is somewhat flatter in shape than 
the other. The largest measures 130 mm. in diameter and 100 mm. high. 
The surface (PI. 39. fig. 23) is covered with conuli crowded together very 
closely. They measure from 1 mm. to 2 mm. high in different parts of the 
sponge, and are usually about 2 mm. to 3 mm. apart, though in some parts of 
the specimens they are even closer together. They are frequently connected 
together by low ridges, so that the whole surface is divided up into meshes 
by them. From their summits the primary fibres of the skeleton project, 
often branching outside the surface of the sponge. 
The oscula are numerous and very variable in size; they are scattered at 
irregular intervals over the whole surface. They measure from 3 mm. to 
10 mm. in diameter. 
The pores are minute, and occur in the meshes formed by the ridges 
running between the conuli, and thus the meshes are a kind of pore-area. 
In some parts of the sponge the pores could not be seen. 
The colour of the sponge is milky white, due to the enormous quantities of 
fine grey-white mud which the sponge has swallowed. 
The texture is soft, and the sponge is easily compressible, but quite tough. 
Skeleton arrangement. (Pl. 41. fig. 27.) 
The skeleton is exactly similar to that of Muspongia irregularis. There is 
‘a definite and fairly regular reticulation of spongin-fibres. The main fibres 
run radially, but not quite straight, and measure 0°08 mm. in diameter. They 
are filled with foreign bodies, which are chiefly sand-grains. The secondary 
fibres are very delicate, and form an irregular reticulation between the 
primary fibres ; they do not contain any foreign bodies whatsoever. They 
vary considerably in size, all sizes between 0:°014 mm. in diameter and 
0:03 mm. being found. The meshwork formed is quite irregular, and no 
average size of the mesh can be given. 
Canal-system and Chambers. (PI. 41. fig. 28.) 
The pores lead directly into a series of horizontal, small canals lying in the 
cortex, which open into large subdermal cavities. These subdermal cavities 
lie quite irregularly in the superficial parts of the sponge, and some of them 
are of enormous size, while others are quite small. From them inhalant 
canals run steeply down into the interior of the sponge. 
The chambers are large, sac-shaped, and eurypylous ; they open by wide 
mouths into large exhalant canals. The mouth is frequently the largest part 
of the chamber, which measures 0:08 mm. to 0°1 mm. in diameter. 
The canals in the interior of the sponge are sometimes very large, examples 
being frequently seen in the sponge 5 mm. or 6 mm. in diameter. 
LINN. JOURN.—ZOOLOGY, VOL. XXXI. 29 
