332 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
species. These pore-grooves are very well marked in the present species, 
quite as wellasin Esperella murrayi, and their skeleton is identical in structure 
with that of the ‘ Challenger’ species. 
The colour of the specimens in spirit is white with a yellowish tinge. 
The interior of the sponge is cavernous and rather lax, and the dermal 
skeleton is not so dense as in Esperella murrayi, otherwise the two species 
are almost exactly similar in skeleton arrangement. 
Skeleton. 
The main skeleton consists in huge bundles of monactinal megascleres 
which spread out on the surface to meet the adjacent bundles. The distance 
between the bundles immediately below the surface is about 1 mm. to 2 mm. 
on the average ; the bundles of spicules average 0°12 mm. to 0°13 mm. in 
diameter. In the interior of the sponge the spicular arrangement becomes 
much more confused, and the bundles are difficult to distinguish. Between 
these spicule-bundles occur large subdermal cavities irregularly arranged, into 
which open the channels from the pore-areas ; from these subdermal cavities 
there leads down into the interior of the sponge a system of large and very 
numerous canals. 
The whole tissues of the sponge are filled with enormous quantities of 
raphides and trichodragmata, with conspicuous rosettes of remarkable aniso- 
chelee near the surface. Small anisochelze of quite another type also occur in 
the sponge, scattered throughout the tissues, and especially abundant on the 
dermal membrane. 
Spicules. 
A. Megascleres. 
The only megascleres are styli which form the spicular bundles referred to 
above. They average 0°5 mm. long and 0:01 mm. in diameter. 
B. Microscleres. 
(a) Chele. (Text-fig. 15.) 
Scattered fairly plentifullvy about immediately below the surface are very 
large rosettes of palmate anisochelee of very striking form. These chele 
form the great distinction between this species and Esperella murray. The 
rosettes are about 0°12 mm. in diameter and contain numerous chele. The 
chele are characterised by the extremely stout and strongly curved shaft 
and by the comparatively large size of the smaller end. The chelee measure 
0:055 mm. to 0°06 mm. in length and 0°032 mm. wide at the widest point. 
Both median and lateral palms are present at each end, and the palms are of 
large size. The lateral palms of the larger end extend some way down the 
shaft in most cases. The shaft is oval in section and measures 0-01 mm. by 
0-006 mm. in major and minor diameters. 
