IQI5.] N. ANNANDALE: Indian Boring Sponges. 19 
which was taken at the same station. The papillae are borne on 
very short pedicels, as a rule only on what may be called the 
upper surface of the sponge; occasionally they are also found on 
the lower surface. I have not been able to detect cellular 
diaphragms. 
Papillae.—Two kinds of papillae have been observed, one of 
which is apparently inhalent, while the other is probably of a 
mixed nature. The latter is considerably larger than the former ; 
its diameter is on an average, in normal circumstances, about 
I mm., whereas that of the smaller papillae is only about 0°4 mm. 
In both cases the vertical walls are straight and the actual papilla 
does not expand much beyond them. The exhalent apertures 
are circular and are protected, as is explained below under the 
heading ‘‘Skeleton’”’, by a peculiar arrangement of spicules. 
Spicules.-—The macroscleres are tylostyles with well differenti- 
ated heads usually spherical in form and frequently containing a 
singlelarge vacuole. The stem is usually curved and spindle-shaped, 
tapering considerably towards both extremities aud consider- 
ably swollen in the middle. More slender tylostyles occur in 
which the stem is much less swollen, but there are also intermedi- 
ate forms. The shape of the head is not constant, for, especially 
in the more slender macroscleres, it is sometimes trilobed and 
sometimes flattened above; occasionally it is even acorn-shaped 
or quite asymmetrical. In the stouter tylostyles the total length 
is on an average about 0°34 mm., the greatest thickness of the 
shaft about 0°02 mm. and that of the head slightly less. 
The nodular amphiasters have both the lateral and the ter- 
minal nodules or bosses relatively large, nearly spherical and 
covered densely with minute straight spines. They are joined to 
the stem, which they often conceal almost completely, by very 
short smooth pedicels. The average length of the spicule of this 
type is about 0°0369 mm. and the greatest breadth across the 
lateral nodules 0:0164 mm. 
The smooth amphiasters with terminal hooks on the lateral 
branches are of the habitual form. ‘heir stem is rather stout and 
the lateral branches taper straightly towards the tip, which usually 
beats about six hooklets. The greatest length of the spicule is 
on an average about o'0164 mm. and the greatest breadth from 
tip to tip of the branches 0°0246 mm. 
The third type of amphiaster, which is very scarce, is about 
the same size as the second, which it resembles considerably, but 
the branches are stouter and bear no terminal hooklets, nor are 
they inflated at the tips. 
Skeleton.—The spicules are arranged to form a skeletal struc- 
ture in a somewhat more regular manner than is the case in most 
species of Clionidae. 
In the horizontal tubules the macroscleres lie parallel to the 
surface and in a large proportion of cases point in the same direc- 
tion. They exhibit, in quite a definite manner, evidence of fasci- 
culation, although in this part of the sponge they do not appear to 
