34 ZOOLOGY OF THE FAR EAST 
All these species are closely related and in order to identify specimens satisfac- 
torily it is necessary to examine the peripherial parts of the colony ; the older zooecia, 
which of course occur towards the centre, are often distorted owing to congestion. 
The genus Hislopia occurs over a great part of Asia. H. placoides is only known 
from Lake Baikal and H. moniliformis (originally described in my volume in the 
" Fauna " as a variety of H. lacustris) from ponds at Calcutta. H. lacustris is widely 
distributed in northern India and Burma and H. cambodgiensis in Indo-China, Siam 
and China ; while the new species H. malayensis has been found as yet only in a 
small lake in the Siamese province of Patani in the north-east of the Malay Peninsula . 
I have recently observed what I take to be remains of a species of Hislopia on shells 
of the genus Aetheria from tropical Africa, probably from the Upper Nile; but these 
cannot be identified specifically. 
Hislopia cambodgiensis (Jullien). 
(PI. I, fig. 8.) 
1880. Norodonia cambodgiensis and H. ■sinensis, Jullien, Bull. Soc. zool. Francs V, pp. 77-79, 
figs. 
I found in Chinese specimens, attached (like the types) to shells of freshwater 
molluscs, that the two forms described by Jullien in the paper cited passed insensibly 
one into the other, his cambodgiensis representing in fact merely older colonies, or 
the central congested part of old colonies, of his sinensis. I can find no difference 
between these forms and H. lacustris, the type-species of Hislopia, that would justify 
generic separation. Indeed, I have long hesitated whether to regard the differences 
that do exist as specific or as merely racial. In the collection of the Indian Museum 
there are specimens of H. lacustris on the shells of Unionidae and Viviparidae from 
jhils (swamps or shallow lakes) in northern Bengal the central or oldest zooecia of 
which agree almost exactly with those of the same kind in colonies from China. 
Moreover, the form of the orifice and the development of spines in connection with it 
are extremely variable characters in both the Indian and the Chinese forms. But 
while in the former the young zooecia are rarely if ever pedunculate, in the latter 
they are invariably so, thus having a very characteristic appearance (see pl.i, fig. 8). 
Other less important differences are the following : — 
1. The colony of H. lacustris invariably forms, when fully developed, owing 
to profuse lateral budding, a solid pavement or layer, whereas in 
H. cambodgiensis lateral buds are produced much less sparingly, so 
that the colony consists of visibly radiating and separate branches. 
2. In H. lacustris (and also in H. moniliformis) the margin of the zooecia 
is thickened and chitinized, whereas in H. cambodgiensis this is not at 
all or very indistinctly the case. 
3. In H. lacustris some at any rate of the zooecia in each colony possess 
four well-developed but short spines at the four corners of the quadrate 
orifice, whereas in H. cambodgiensis the orifice is usually subcircular 
and spines are only occasionally developed in connection with it. 
