142 Records of the Indian Museum. [VoLre Vin; 
Plumatella tanganyikae that I realized the complexity of the 
opercular apparatus in this species, but once this had been realized, 
it was not impossible to trace the same structures in preserved speci- 
mens from both Africa and India, although the much paler colour 
of the ectocyst in the former made the observat:on more difficult 
than it was in the case of Indian examples of the species. The 
peculiarities described in the preceding paragraphs would fully 
justifv the recognition of P. tanganytkae as the type-species of a 
distinct genus, were it not for the fact that the different species of 
Plumatella (s. s.) exhibit considerable variation in respect to the 
manner in which the orifice is closed. In those species (e.g., P. 
repens and P. fruticosa) in which the zooecial wall is fairly flexible 
and there is no furrow along its dorsal surface, the polypide is 
merely withdrawn by the retractor muscles, in the same way as 
the tip of the finger of a glove might be withdrawn by pulling 
strings attached to its internal surface. The walls of the zooecium 
collapse together and the result is a rounded tip with a minute 
round aperture in the middle. In those species, however, (e.g., 
P. emarginata and P. diffusa) in which the external ectocyst is 
somewhat inflexible, a furrow (that is to say, a narrow longi- 
tudinal area on which the ectocyst is thinner and softer) extends 
from the orifice along the dorsal surface of the zooecium and 
forms at one end the dividing line between valves not dissimilar 
to those which close together over the tentacle-sheath in P. tangan- 
yikae. ‘The lophophore emerges between them just as it does in 
that species. In P. tanganytkae there is usually no furrow on the 
distal end of the zooecium proper, although there often is one on 
the proximal part: but occasional zooecia may be found in which, 
in the absence of a dorsal hood, the soft integument of the valves 
and the separation between them extend for a short distance 
along the dorsal surface of the zooecium. Even in such zooecia, 
however, the separation between the stiff zooecial wall and the 
soft opercular part of the ectocyst is much more clearly defined 
than it ever is in such species as P. emarginaia. 
P. tanganvikae must be recognized as the type-species of the 
new subgenus Afrindella, for it is not certain, though highly 
probable, that a similar method of closing the zooecium occurs in 
Kraepelin’s P. philippinensis, which in other respects appears to be 
closely related. 
5. PLUMATELLA (AFRINDELLA) TANGANYIKAE, Rousselet. 
P. tanganyikae, Rousselet, P.Z.S., 1907 (1), p. 252, pl. XIV, 
figs. I-4 
P. bombayensis, Annandale, Rec. Ind. Mus., II, p. 169, 
OS. Ae 322 
P. tanganyikae, id. Faun. Brit. Ind., Freshwater Sponges, 
CLC. Pp: 225. 
I do not think that the form I described as P. bombayensis 
can be distinguished specifically from Rousselet’s African species, 
