OF SOUTHERN INDIA. 399 
through all the successive formations, but they never are very common or very 
numerous, with the exception of a few from brackish water deposits. With regard. 
to the classification of the cretaceous species I shall defer my remarks to the end, 
after having given previously a review of the genera. Seeing the great con- 
fusion, already existing, introduced by some recent comments on evidently imperfect 
figures, it will be advisable not to make any essential changes in the generic 
‘determination, unless specimens of the same species or the originals have been 
examined. The following are the principal generic forms constituting this sub- 
family. 
1. <Acteonina, dOrbigny, 1850. Shell turreted or ovate, moderately thick, 
with more or less elevated spire, inner lip flatly thickened at the edge, not plicated 
or twisted, aperture evenly rounded in front; the last whorl being always anteriorly 
somewhat suddenly contracted. The surface of many Acteonine appears to be 
perfectly smooth, but it is more likely this is only in consequence of the uppermost 
punctated layer of the shell having been removed; transverse ribbings are com- 
paratively rare, and if present they generally become obsolete on the last whorl. 
Meek (1. cit., p. 91) proposed for species, like Act. ventricosa, d’Orb., and others, 
being merely distinguished by a shorter spire and a more inflated last volution, 
the sub-generic name Trochacteonina. When, however, we examine a large 
number of specimens of any of the species of Acte@onina (or Trochacteon, Acteo- 
nella olim), we may be certain to find among them some which are more cylindrical, 
others which are more inflated at the last volution, and the last form is almost 
invariably connected with a shorter spire. Thus we observe variations which hardly 
can be considered as being constant in a species, and it seems to me, therefore, that 
they ought not to be used in distinguishing genera, though they may under cir- 
cumstances have a specific value and sometimes be of great importance for local 
faunas. There is a continued series to be traced from such forms, which have the 
spire plane, or even a little immersed ( Orthostoma conulus, Buv., Stat. de la Meuse, 
ete., pl. 24, figs. 16-17; or Act. brevis, Lyc. foss. Great Ool. Suppl., pl. 41, fig. 6), to 
those which have the same slightly (4cteon. ventricosa, VOrb., or Act. Luidii, 
Morris), or more strongly elevated (Act. sparsisuleata, d’Orb.), and from these again 
to forms in which it almost exceeds the last whorl in height. 
The species of Acteonina begin in the carboniferous formation, being most 
numerous in the jurassic period, but they decrease very considerably in the cretace- 
ous, continuing, however, up into the eocene formation, for the Ampullaria problem- 
atica, Desh. (Paris fossils, II edit., pl. 36, figs. 1-2) must be considered as an 
Acteonina, and Deshayes besides describes an Orthostoma conovuliformis (Par. foss., 
T ed., pl. 6, figs. 9-11). 
Deshayes claims (Paris fossils, II ed., II vol., p. 613) the priority of his name 
Orthostoma against that of Acteonina, the former having been published first 
in 1842; but long prior to this in 1831, and afterwards in 1834, the same name 
was applied to totally different animals by Ehrenberg and by Audouin; consequently 
d’Orbigny’s name for these shells must be retained. 
