10 CRETACEOUS GASTROPODA 
two whorls being smooth, and proportionally larger or wider than the following. 
These are distinctly convex, separated by an impressed suture and obliquely and 
transversely striated, the strive disappearing on the sides and on the base of the 
last whorl. The latter has its greatest width above the centre, becoming gra- 
dually narrower towards the umbilicus, the margin of which is in the adult and 
perfect shell evenly rounded, while in the young shell it is angular or even 
carinated, as shown in figure 2, Pl. I. The width of the umbilicus at the base 
amounts to about one-third of the whole basal diameter; but as not more than 
a portion of the preceding whorl could be exposed from the adherent rock, it 
is uncertain whether more volutions are visible in its space or not. In any case 
it is certainly very narrow lower inside. Further, the last whorl is near the mouth, 
laterally and somewhat below the middle, strongly contracted or compressed. 
(Fig. 8.b.) To this contraction correspond two strong teeth inside, which have two 
equally formed teeth corresponding on the opposite inner lip. The upper of these 
teeth is much stronger, short and bipartite, the lower is fold-like, thinner and 
longer. Besides these, there are on the upper portion of the inner lip two other 
thin fold-like plaits, and one near the suture on the outer peristome. ‘These three 
folds are seen in several of our specimens, but in none extending far inside of the 
whorl. Close to the aperture, which is of semilunar shape, the last whorl is again, 
as before, regularly expanded or a little inflated and somewhat deflexed. The outer 
peristome itself is scarcely enlarged and reflexed, its plane having a position very 
oblique to the axis of the shell. . 
Localities. Neighbourhood of Comarapolliam, at Ninnyoor and Veraghoor ; 
at the first locality rather common in soft light coloured sandstone. 
Formation. Arrialoor group. 
2. ANCHISTOMA ARRIALOORENSE, Stoliczka. Pl. I, Fig. 6. 
A. testa discoidea, late umbilicata, spira vix elevata; anfractibus quinis, tereti- 
bus, supra convexis, sutura tmpressa junctis, obsolete transversim striatis, lente 
crescentibus ; ultimo antice deflexo, basi rotundato, prope aperturam parum con- 
stricto ; apertura perobliqua, ovate rotundata: peristomate exteriore expanso, angu- 
latim reflexo ; interiore anfractu penultimo adherente, moderate calloso. 
Height of the shell : transversal diameter (taken as 1-00) 500 Hoc eon GY) 
Width of one whorl above: transversal diameter jae noc 500 coo WPS} 
The shell of this species is nearly discoid, the spire being hardly elevated, but 
the umbilicus is, so far as it could be traced, very large, occupying nearly half of the 
total width of the basis. The surface of the shell, which appears to have been very 
thin and pellucid, is only very finely striated transversely. The whorls are five in 
number, convex above, separated by a deep suture and very gradually increasing 
in breadth. The last whorl is widest somewhat above the centre and then evenly 
rounded into the space of the umbilicus; near the mouth it is strongly deflected 
being at the angle of deflection somewhat constricted. The aperture is conse- 
