OF SOUTHERN INDIA. 49 
handled, they may replace satisfactorily a perfect shell, as impressions of the shells do 
so generally. In other cases, however, they are of little use indeed, and if they do not 
admit even generic determination approximately, they ought justly to be rejected. 
Among the casts of crprarys this is often actually the case, the thickened shell 
with its surface being totally removed, we get a smooth cast, which can give the 
shape of the true shell only approximately. There is one favorable condition to be 
mentioned, that is, if the aperture be filled up with stone, this preserves usually 
the impressions of the teeth on the margins of the peristome. 
As the anterior portion of the shells is often much compressed, leaving 
internally a very small space, this prolongation is in the greater number of cases 
even not filled with the rock mass at all, or if it has been, it breaks with the 
greatest ease, without leaving any peculiar marks of its previous existence. This 
case may be seen on Cyp. Newboldi, or Kayei, on Pl. IV, and therefore it is, tha 
such casts are usually much shorter than the original shell has been. All these 
difficulties are not seriously felt in determining neogene species, on account of the 
softer materials, in which they generally occur, but they have to be accounted for in 
the eocene, and great care must be taken in the determination of cretaceous species, 
for which reason alone we have specified them here. 
The species which belong to this sub-family have been and are in general up to 
the present time described under the single generic name of Cyprea. Gray has after 
several repeated attempts at last succeeded in grouping the principal characters 
of the numerous species, and he divides the crpr#zv# accordingly into several 
genera, some of which he takes as co-ordinate, others as sub-ordinate. The fol- 
lowing genera, quoted by H. and A. Adams, are proposed; Aricia, Inponia, Cyprea, 
Cypreovula, Trivia, Pustularia, Epona. Naria appears doubtful, but there seems to 
be rather a necessity of one or two generic separations among the small and smooth 
species, which are partly referred to Cyprea, partly to Laponia and Trivia. Included 
in this sub-family ought to be, we believe, Hrato, Risso, and Pseudocassis, Pict. et 
Camp., and excluded, Marginella. 
The most apparent characters of the different genera are as follows :— 
1. Aricia are pear-shaped shells, dorsally and posteriorly gibbose, and flattened 
below; in form they are most closely related to Calpurnus of the orvziv“; Aricia 
moneta is the best known shell of this type. 
2. Luponia are globose, oviform and pear-shaped shells, below with convex 
margins of the aperture; the best known shell of this type is L. tigris. 
3. Cyprea inthe stricter sense includes the cylindrical forms with usually a 
thinner shell and conspicuous spire, of which Oyp. argus and. testudinaria may serve 
as the best examples. 
Connected with the difference in form of these three generic groups, there is 
always some kind of alteration in the dentition of the aperture, and it is carefully 
recorded by Gray. Several of the smaller specimens, partly distributed under Luponia 
and Cyprea, partly referred to Trivia, offer, as we have already noticed, some difficulty 
in being entered among these genera, and they will no doubt receive due attention. 
10) 
