eve beeen A SY M BPO PR ewerEN DIC A. 
No. 3.—POLYZOA ASSOCIATED WITH CERTAIN 
GANGETIC TORTOISES. 
By N. ANNANDALE, D.Sc., F.A.S.B., Superintendent, Indian 
Museum. 
(Plate XIII.) 
It was noticed that peculiar lichenoid patches were present 
on the carapaces of a number of tortoises captured in the Ganges 
near Rajmahal in March, rgr2, by Mr. B. L. Chaudhuri and brought 
alive to Calcutta At firstsight the patches were taken for algae, but 
a close examination showed that they were formed of one or both 
of two species of polyzoa, namely Hislopfia lacustyis and an un- 
described form of Plumatella closely allied to P. tanganyikae. 
The tortoises in the collection belonged both to the Testudinidae 
and the Trionychidae, the former being represented by three 
species of Kachuga (K. dhongoka, K. lineata and K. smuthit) 
and one of Hardella (H. thurgit), while the Trionychidae comprised 
Trionyx gangeticus and T. hurum. ‘The polyzoa were not found on 
either species of Tvionyx or on K. smithit (a small species), but 
one or both occurred on most of the larger sp2cimens of Testudi- 
nidae.. Probably the skin of the mud-turtles is too soft and slimy 
for their proper attachment or growth. 
The tortoises had heen out of the water for at least twenty- 
four hours before they were examined and the polypides of the 
poiyzoa had perished, but fortunatelv the zooecia remained in 
. sufficiently good condition for an investigation of the general 
structure and specific characters. 
HISLOPIA LACUSTRIS, Carter. 
Annandale, Faun. Brit. Ind.—Freshwater Sponges, etc., 
pp. 190, 200—205, figs. 35A, 38 and 309. 
The zoaria on the tortoises’ shells each cover an area of 
several square inches and are of luxurious growth, almost every 
zooecium producing its full complement of three buds and the 
whole colony being closely compacted, without, however, the 
zooecia ovetlapping. ‘The individual zooecia are small, measuring 
on an average slightly over 1 mm. in length and being very vari- 
able in breadth ; they are as a rule irregularly polygonal in outline 
and have the proximal end narrower than the distal. The orifice 
is circular or subcircular and asa rule lacks spines, although it 
