134 lontributions to Indian Malacology. [No. 2, 
Contributions to Indian Malacology, No. VII. List of species of 
Unio and Anodonta described as occurring in India, Ceylon and 
Burma.—By Wiiu1am T. Buanrorp, A. 2. S. W., F. G.S. 
[Received 5th September, 1866. | 
There are few genera in the whole range of natural history more 
puzzling than Unio and Anodonta. Every naturalist who has at- 
tended to them has been struck by the great variation of which the 
different species are susceptible, though it is to be regretted that this 
knowledge does not appear to have had much influence in restraining 
some naturalists from recording as distinct species isolated specimens 
which reached them from distant conntries, and which only differed 
from other specimens in characters of very doubtful specific value, 
Although the Unionide of the Tudian waters are far behind those 
of some countries, and especially of America, in the amount of vari- 
ation which they exhibit, amply sufficient is shewn to render them 
very difficult to classify. And as the question of variation is one of 
the most important, especially at the present day, in the whole range 
of zoological science, those animals which, in the wild state, exhibit 
the greatest amount of variation, are peculiarly worthy of study. 
In endeavouring to classify the Indian shells, one great difficulty 
that Ihave found, has been the determination of described types. 
Descriptions of Indian Unionide are scattered through many works, 
not easily procurable in India. There are, probably, yet a few to 
which I have not had access, but as I have been able to compile a 
list, comprising, I believe, a very large majority of the published 
forms, I think that I shall be aiding any one who, in India, may be 
engaged in the same study, by printing the list, with references to the 
original descriptions and to figures, whenever such exist, and by 
adding such remarks as appear to be necessary. 
I also hope to be able to publish figures of a considerable propor- 
tion of the species named ; in some cases, copies of the original illus- 
trations; in others, drawings of authentic specimens. I shall feel 
greatly indebted to any one who will aid me in this endeavour by 
furnishing me with typical forms, or with any specimens from distant 
parts of the country. In all such cases, a small series of the varieties 
and different ages is desirable. 
