African Freshwater Sponges. 97 
scattered over parts of the shell now free from the sponge, 
They are firmly attached to the shell and rest on a dense 
mass of gemmule-spicules, 
Spicules—The macroscleres are slightly curved, stout, 
smooth oxea, tapering abruptly at each end to a small sharp 
point into which the axial canal extends. The spicules are 
slightly swollen at the ends, and sometimes there is a faintly 
marked swelling at the centre of the shaft. There are not 
many abnormal forms present, but some of the spicules are 
irregularly bent and occasionally one end is rounded off. 
More rarely both ends are rounded. The macroscleres 
measure 0:275-0°335 mm. in length and have a thickness 
of 0°02-0:027 mm. They resemble in some degree the more 
pointed macroscleres of Spongilla crassissima, Annandale, 
var. crassior, Annandale, but they are more swollen at the 
ends and are somewhat longer and thicker. 
There are no free microscleres present in the sponge. 
The gemmule-spicules are short, thick strongyla provided 
with strong spines. Some of the spicules, especially the 
shorter ones, are swollen in the middle, so that they are 
barrel-shaped ; others are nearly spherical, but still beara 
few spines. The spines are grouped at either end of the 
strongyla, leaving the centre of the shaft smooth, but often a 
few scattered spines occur along the shaft. ‘The spines are 
stout ; typically they are strongly curved towards the centre 
of the shaft and end in a sharp point; but many of them are 
stout, straight, knob-like projections. The spicules measure 
from 0°035-0°1 mm. in length and have a thickness of 0°012- 
0016 mm. Some of the short inflated ones are as much as 
0-021 mm. in diameter. 
Locality. Benguela; on a shell of Atheria elliptica, var. 
tubifera. 
Spongilla (Stratospongilla) benguelensis, sp. n. 
Tie sponge occurs in a number of very small patches 
towards the edges of the lower valve of the itherva shell on 
which the previously described species is growing. ‘There 
are the remains of various other patches of the sponge also on 
the lower valve in the region of the hinge and one or two 
minute specimens on the upper valve. These patches of 
sponge are very inconspicuous, as they run chiefly in the 
furrows of the shell; in the dried state they are soft to the 
touch and their surface is even. Scattered over parts of the 
lower valve of the shell are quite a number of gemmules 
belonging to this species. Hach gemmule is firmly fixed to 
Ann. d& Mag. N. Hist. Ser. 9. Vol. iii. r; 
