OF SOUTHERN INDIA. 279 
volution, on which the transverse ribs become obsolete, is considerably produced and 
spirally striated, the more central strize being the strongest. The aperture is ovate, 
oblique, anteriorly somewhat produced, and obsoletely effuse; the inner lip thick, 
especially posteriorly ; the columella distinctly twisted; the outer lip with a strong 
external varix. 
Locality—N. E. of Odium, in brown calcareous sandstone; only one, but 
almost perfect specimen has been found. 
Formation.—Ootatoor group ;—principal beds of Ammonites rostratus, (inflatus) 
Sow. 
LIX. RISSOINA, d’Orbigny, 1840. 
Char. Riss. testa elongate turrita, acuminata, sepe striis spiralibus atque 
costulis transversulibus ornata, rare levigata; apertura obliqua, integra, postice 
acute-angulata et angustata, antice effusa; labro sinuato, versus basim producto, 
extus incrassato ; columella solida, antice truncata seu plus minusve abbreviata. Oper- 
culum corneum, sub-spiratum, intus cornutum. (Vide Denksch. Akad., Wien, 1861, 
XIX, pt. IT, p- 102). 
The distinctions between most of the recent species of Rissoa and Rissoina 
are very distinctly traceable through the characteristic form of the aperture, and 
the same distinctions also apply to the fossil ones. Deshayes, in his last edition 
of the Paris fossils, only accepts the genus Rissoina with great hesitation, 
stating that it is very difficult to distinguish in fossil species, whether they belong 
to Rissoa or to Rissoina, He justly points to the few instances, in which the 
operculum of a Rissoina has been made known, but I rather think that all these 
difficulties of generic determinations in fossil Conchology chiefly arise from the 
insufficient preservation of the specimens. 
Schwartz von Mohrenstern considers all the species older than tertiary, as being 
rather doubtful. There may be some good reason for this, but I do not see the 
impossibility that Rissoime may not have existed even long prior to the cretaceous 
period, though from this formation only two species have as yet been reported ; 
R. incerta, VOrb. (Pal. frang. erét., II, pl. 155, figs. 11-18), and R. Jaccardi, 
Pict. et Camp. (Mat. Pal. Suisse, 3me. Ser. Foss., Ste. Croix., p. 348, pl. 74, fig. 1). 
Guéranger (Essai d’un rept. paléont. du dept. Sarthe, etc., Mans., 1853, p. 29,) 
names a species, R. Cenomanensis, but I suspect it is the same which he afterwards 
figures as Hulima Cenomanensis, though he does not say so, (see Album pal. dept. 
Sarthe, etc., le Mans., 1867, pl. 9, fig. 13). The species is evidently, however, neither 
a Rissoina nor a Hulima, but a true Keilostoma. 
We have to report from South India one’ species, which is identical with a 
shell described by Prof. Miller from the upper cretaceous beds near Aachen. 
