REMARKS. Xiil 
geological position and the probable conditions, under which the respective fossils 
lived and were buried, ought to be always correctly ascertained. As scon as 
our paleontological materials are more complete, such a series of shells will 
prove highly instructive. We have to compare then the series of each successive 
formation with the preceding, note the changes of form with reference to that 
of organisation, inquire into the causes which may have produced these, and 
deduce from this the direction, plan and degree of progressive development. Such 
a thorough examination of the entire fossil and living order of the Mollusca 
in one locality, or rather so to say in one basin, or geographical area, would give us a 
better and firmer basis for a natural system than anything else, and when such in- 
quiries have been in reality, so far as possible, extended over the entire globe, we 
shall have then in hand at least a portion of the materials, which we require for 
that system. We must, of course, necessarily be contented with a certain number 
of typical forms, for to obtain all the fossil species which have existed is almost 
beyond our expectation. 
This is the principal reason why, in describing a large local fauna, we 
thought it right to take advantage of the opportunity for the proposition of a few 
systematical changes. 
In conclusion I ought probably to say a few words in justification of the 
great length to which my memoir on the Gasrropopa has been extended. 
It was indeed only after mature and repeated considerations, that I entered 
upon the difficult and laborious task of making references to the recent fauna at 
all. When, however, I found the necessity for adopting a large number of generic 
names instead of one, as used by several other paleontologists, the further neces- 
sity arose of grouping these into families and so on. In giving occasionally a review 
of the cretaceous genera and species of a family already known, it was almost 
impossible not to mention at the same time other recent genera of the same family. 
In this way the bulk of the information increased, and I afterwards thought it 
useful to give, besides, a brief review of the zoological character of each family 
or sub-family if necessary, so as to aid, even slightly, the student of Conchology in 
India, where the desirable means of reference are not so easily procurable, as they 
ave in almost every large town in Europe. 
Several other additions and explanations of little known genera of shells will 
perhaps be welcome even to some of my colleagues in the study of Conchology, 
F. STOLICZKA. 
CaLcUrrA, 
Marcy 1867. 
