Vol. IX, No. 1.] Sponges of the Lake of Tiberias. _ 63 
[W.S.] 
Galilean forms are described below ; but I am not fully satis- 
fied that they are actually congeneric. ‘Three species from 
Central Africa (S. tanganyikae and S. moorei, Evans, and 
S. (4) cunningtoni, Kirkpatrick) and at least one from Gelebes 
(S. (@) — Weltner) should also be assigned provisionally to 
the g 
Nudospongilla reversa, sp. nov. 
(Plate ii, fig. 2; plate iii, figs. 2, 2a; plate v, fig. 3.) 
ponge hard but friable, forming crusts or lamellae on the 
delicate chitinous membrane. On the upper surface there are 
broad, deep, patent oscular grooves which are not covered by 
the dermal membrane except at their narrower extremity, 7.¢. 
at the extremity furthest from the larger exhalent apertures. 
The main efferent channels open directly into the sides of these 
grooves, running a slightly oblique, but ee horizontal 
course through the substance of the nge. Some of the - 
channels measure as much as 3 mm. in iiarcter the greatest 
depth of the grooves is 4mm. and the greatest width 5 mm 
‘hen the surface of the sponge is examined with a lens the 
the main horizontal channels the network is of a more definite 
nature, but the vertical fibres are not much more distinct than 
the transverse ones; at first sight both appear to be thick, but 
a closer examination shows that each fibre is composite, con- 
sisting of at least two strands not quite parallel to one another. 
The spines on the surface consist of much more slender fibres, 
as a rule not more than three spicules thick, projecting upwards 
through the dermal membrane. At the base of these fine fibres 
there is a distinct horizontal network of iplutiles, but it is not 
thickened or compressed to form a cortex. The meshes of the 
skeleton are small throughout. There is not very much chiti- 
nous matter present. 
Spicules.—The skeleton-spicules are short, smooth, moder- 
ately stout wo feebly hey and by no means sharply 
pointed. ey ro o 0°34 mm. long, but the 
majority are approximately of a sca length ; ay greatest 
transverse diameter varies from 0-024 to 0°029 m few 
smaller and more sharply painbed amphioxi occur in ‘all spicule- 
sl praia sana but these lie loose in the interstices of the skele- 
n, and are probably immature or abortive spicules. 
