OF SOUTHERN INDIA. 9 
Considering these and other points of distinction H. and A. Adams quote five 
subgenera, which, however, do not seem to be as well defined as appears necessary. 
To make these separations of real classificatory value, it is absolutely necessary, 
that they be based upon the examination of the animals as well as the shells, so as 
to be certain whether the respective organs can in any way be depended upon as 
to their constancy. Meanwhile we prefer to describe the cretaceous species under 
the more extensive heading of Anchistoma. 
The greater number of living species of Anchistoma is known from America 
and Europe. From India there are only a few species described for some of which 
Adams proposed the name Corilla (in place of Atopa, Albers). Mr. Benson includes 
under this name mostly South Indian and Ceylon species only, while for some 
others, chiefly from Burmah and North India, he proposes a second name, Plecto- 
pylis, based upon a difference in the pylaic plication. (Vide Ann. Mag. Nat. Hist. 
1860, III, Ser. Vol. V, p. 248.) It appears that the species were in former periods 
nearly as numerous as they are at present in India. We describe three, namely, 
A. cretaceum, Arrialoorense and Arcotense, all of which are new, and the first, 
apparently rather a common shell resembling in form European species, while the 
two others have up to the present been found only in single specimens also partly 
resembling species from Europe, but in general form next to the Indian Plectopylis. 
Several Anchistoma are known from the tertiary deposits of Europe. 
1. ANCHISTOMA CRETACEUM, Stoliczka. -Pl. I., Figs. 1—5. 
A. testa conico-depressa, spira parum elevata, apice obtusa, mamillata, late 
profundeque umbilicata ; anfractibus senis, angustis, lente accrescentibus, convexis, 
sutura timpressa junctis, supra transversaliter oblique striatis ; ultuno prope aperturam 
lateraliter constricto atque rursus expanso, vix deflexo, striis subtus evanescentibus, 
wm etate adulta ad wmbilict marginem rotundato, juniore carinato ; apertura obliqua, 
rotundate semilunart, intus dentata atque obsolete plicata; labro atque labio prope 
aperturam bidentato, dentibus superioribus crassioribus et bifidis, inferioribus elongatis 
pliciformibus utringue ad angulum posteriorem peristomatis nonnullis plicis tenuibus 
munitis, peristomate exteriore vix reflexo. 
Largest specimen in our collection from Comarapolliam measures 8°5 mm. in 
height and 20 mm. in width. 
a. b. Cc. 
Height of the shells: transversal diameters (taken as 1:00), 043 0-51 0°54 
Width of outer whorl above: transversal diameter ... a06 0:18 O17 O18 
a, b,c, being specimens figured in Figs, 4, 5, 3, respectively. 
As to form, this fine species resembles the American Anchistoma auriculatum, 
Say, which has very nearly the same number of equally narrow whorls. The spire 
is in our species more or less elevated, but not exceeding an angle of 130 degrees. 
The increase of the whorls is very gradual; the first or embryonal one or 
D 
