INTRODUCTORY REMARKS. 
WHENEVER a large number of different natural objects is to be described, it is 
always most desirable, that this be done according to some certain systematic ar- 
rangement. In paleontology, where the fossil forms are sometimes so very differ- 
ent from the living ones, such an arrangement is almost indispensable, as it is the most 
essential guide to understanding the relationship between the present and the former 
organisms. It is well known that, although species, genera, and other higher divi- 
sions of the animal kingdom have become extinct during the course of time, they 
still form a part of one universal system of organic life on our planet. The 
principal task, therefore, of the paleontologist is clearly to examine these fossil 
remains with reference to their relations to existing forms, and thus, in co-operation 
with the zoologist, gradually to furnish the materials for a true natural system in 
the animal kingdom. 
In bringing before our readers the descriptions of the Gastropodous remains 
of the South-Indian cretaceous rocks, we have tolerably extensive and varied mate-~ 
rials to deal with. It may, therefore, not be out of place to offer, first, a few 
remarks on the classification of the Mollusca in general and subsequently on 
that, which is to be adopted in our present more special and limited case. 
Several conchologists regard the GAstTRopopA as the most highly organized 
of the Mollusca; and taking into consideration that they include forms with 
usually a well-developed head, organs of generation and of respiration, etc.,* 
this classification will appear by no means unfounded. The Cephalopodous 
form is certainly of a type lower in its organization, but it had attained, so to 
say, the maximum, or at least a much higher grade, of development in a certain 
direction, or upon a certain plan, in which gradual progression seems to have 
taken place in the organization of the Mollusca. The functions of several organs in 
the CePpHALOPopDA—those of the central nervous, as well as others of the muscular 
and the generative systems—in general appear, however, to give to this class a 
higher place in the general arrangement of the Mollusca than to the GasTRopopa, 
and on this account it was that the former obtained, especially since the times of 
Lamarck and Cuvier, the first rank among the Mollusca. A careful comparison of 
the different systems, which had at various times been proposed, will be found in 
* Many of them being air-breathers solely. 
