IQI5.] N. ANNANDALE: Parasitic Sponges. 465 
external surface is outermost is due to the fact that they have 
grown round projecting fragments of coral at the angles of the 
Clionid’s galleries and that these fragments have disappeared 
owing to the action of the acid. 
Spicules.—There are three kinds of spicules, viz. (a) com- 
paratively stout, smooth styli of the type called rhabdostyles by 
Topsent! in his definition of the genus, (0) much more slender, 
almost hair-like tylostyli, which are shorter than the longest 
rhabdostyles and (c) small, much contorted sigmata. 
The rhabdostyles are perfectly smooth and have their heads 
almost truncate, not at ail swollen and as a rule spirally contorted 
in two whorls. They are actually rather slender and vary greatly 
in length; indeed, two series may perhaps be distinguished as 
regards size, but intermediate forms occur. Those of the larger 
series are on an average about 0176 mm. in length; those of the 
smaller series not more than 07099 mm. ‘The shaft tapers gradu- 
ally to a fine point. 
The dermal tylostyles are curved or sinuous, perfectly smooth, 
very slender and almost hair-like in appearance; they are longer 
than the shorter rhabdostyles. Their heads are of an elongate 
oval form and often not at all clearly differentiated. 
The sigmata are fairly uniform in size, small and slender, vari- 
able in shape but never having a complete twist or knot in the 
centre and never enlarged at the extremities. 
Skeleton.—The skeleton is very degenerate and the number of 
spicules present is comparatively small. The rhabdostyles stand 
separate and semi-erect, with their contorted heads resting on the 
basal membrane and their shafts pointing obliquely upwards. 
The tylostyles lie horizontal in ill-defined bundles, which are 
often comparatively broad and sometimes form as a whole well- 
marked curves, but are never reticulate. The sigmata are scat- 
tered sparsely without definite arrangement. The slender tylo- 
styles are more numerous than either of the other two kinds of 
spicules. 
Measurements of Spicules. 
Length of rhabdostyles .. .. 0°0902-—0°209 mm. 
Diameter of shaft of rhabdostyles .. 0°0057—0'0082 ,, 
Length of slender tylostyles oe OL LAG: mitt. 
Length of sigmata ee ang 001235, 
Type.—No. 6420/7 ZEV, Ind. Mus. (mounted in Canada 
balsam on a slide). 
Locality.—Port Mouat, Andaman Is., Bay of Bengal (‘ Investi- 
gator’). 
The type-specimen occupies the galleries of Cliona viridis in 
a piece of dead Madreporarian coral. The external surface of the 
| Rés. Camp. Sci. Monaco, fasc. 11 (Spongaires de l’Atlantique Nord), p. 115 
1892). 
