OF SOUTHERN INDIA. 7 
could, by occasional higher tides or higher reach of the waves, have been without 
any difficulty carried away to greater or lesser distances from the shores, and there 
buried with the marine inhabitants of the place. Similar cases occur in the tertiary 
deposits also, as has been noticed by Deshayes in the Paris basin, and by Dr. M. 
H6érnes in the Vienna basin. With regard, indeed, to the Helix Turonensis, Desh. 
of the latter basin, it has been proved that the species survived the marine fauna 
with which it occurred. The species continued to exist on unaltered, although the 
sea had disappeared from the shores which it inhabited, since it has been found fossil 
in the marine, brackish and the fresh-water deposits of one and the same place, 
where these deposits can be very clearly seen to have succeeded each other. 
This is a point of very high interest and of great importance in attempting 
to trace out the changes of climate, and other correlated phenomena, towards the 
close of one and the commencement of another formation. When we can establish, 
that the terrestrial fauna did not change during two successive periods, in which 
considerable changes and distribution of sea level took place, we can conclude with 
tolerable certainty, that the climate of the place was, during both these periods, 
pretty nearly the same, and also, that if any changes have taken place, they must 
have occurred by so slow a process, that the animals could easily acclimatise 
themselves. Sudden changes in the terrestrial faunee would lead us to suspect 
some rapid alterations in the climatal conditions and configuration of the land, 
and probably an equally sudden change in the neighbouring waters. But our 
physico-geological investigations are still too deficient to enable us to define the 
limits, within which terrestrial changes have affected the organic life of the adjoin- 
ing seas and vice versd. It is, however, certain that much knowledge may be 
anticipated from careful local enquiries and thorough examination of special basins. 
Instances of an admixture of land with marine shells occur still on the shores of 
almost every sea, more especially where banks with shallow water exist. 
Of the four species to be here described, Anchistoma cretacewm was more 
common: the other species were very rare, but although only known from single 
specimens, these are mostly sufficient to enable us to characterize the species, and, 
therefore, are well worthy of notice. This will also, I hope, induce subsequent 
observers to devote greater attention to these very interesting shells. It can 
scarcely be doubted, that a careful search in these deposits would largely reward 
the observer, by adding to the number of cretaceous land,—and probably fresh-water,— 
shells also. 
H, and A. Adams unite, under the sub-family of Helicine, a number of 
genera into which Lamarck’s genus Helix had been divided. It is well known, 
that Linneeus included, under Helix, besides the common land-snails, many fresh- 
water and even marine shells. Subsequent naturalists, and especially Lamarck, 
defined and restricted the genus more carefully, and among others Pfeiffer made it 
an object of his special study, the results of which are well known through his 
able monograph of the Helicide. In his earlier publications, Pfeiffer strictly 
defended the unity of Lamarck’s genus Helix, in his later researches he does not 
