INTRODUCTION. v 
Drawings of the animals will also be added, with the ana- 
tomy whenever it can be obtained, showing the odontophore 
&c., by the help of which I trust we shall be able to arrive at 
some better-defined system of classification to what we have 
now, based solely on shell-characters. We shall then be 
better able to understand the relationship between our Indian 
genera and those of the neighbouring regions which are 
being worked out on one side by Professor von Martens and 
O. Semper, and on the African &c. by Professor A. Morelet, 
J. R. Bourguignat, aud many other foreign conchologists. 
Not the least important part of the work will be attention 
to the record of accurate distribution of species; and I shall 
always give the exact locality and districts of India, with 
elevation &c. 
I shall not limit myself to political boundaries, or what is 
termed British India; such boundaries are being constantly 
altered or overstepped by the naturalist; the progress of a 
friendly mission or the entry of a punitive force into some 
adjacent independent country brings a fresh crop of objects 
of natural history. I therefore take as a northern limit the 
watershed of all the rivers that flow into the Indian Ocean 
through the countries named on the titlepage ; thus the Indus 
will include the whole of Afghanistan and Kafiristan, Swat, 
Gilgit, Baltistan or Little Tibet, Ladak, Rudok up to the 
Manasarowa Lake. The Brahmaputra will include that vast 
unknown country northwards and eastwards of the junction of 
the Dihong and Dibong rivers, any part of which we may see, 
and I hope to see, explored within the next four or five years, 
and the same of the Irrawaddy and Salween, while the southern 
extension of the Mulé-it range, in Tenasserim, down to the 
Malay Peninsula, gives a very well-defined boundary in that 
direction. I have included South Arabia as far as the vicinity 
of Aden, because on that side we have a mingling of East- 
