OF SOUTHERN INDIA. 253 
and the aperture was probably simply rounded without any insinuations. This 
genus evidently exhibits, as regards the form of the shell, the greatest relation to 
the Vierueripm and Srir1gvarupm. The few species known are paleeozoic. 
6. Straparolus, Montfort, 1810; (Huomphalus, Sowerby, 1812, or 1814), 
and 
7. Bifrontia,* Desh., 1833 (Anm. s. vert. Foss. Paris, 1. ed., pt. II, p. 221; 
2me. edit., Vol. II, p. 677). 
a. There could scarcely be greater difficulties to overcome in the classification 
of the old genus Helix, than are met with in that of the shells, known to palzeon- 
tologists under the above two or three names. No two publications are to be 
found, which agree in the signification of these names and the limits of the genera 
or groups of shells, to which they ought to refer. It cannot be questioned, that 
the name Straparolus of Montfort has priority before that of Huwomphalus, though 
the latter has been applied to different species, but the former was certainly 
not unknown, even if unjustly neglected like many other names of the same 
author. When we compare a series of specimens of the well known Strap. 
(Huomphaius) Dionysii or pentangulatus and others, we can observe, that the strize 
of growth are on, or near the upper keel, distinctly insinuated backwards, and on the 
periphery bent in the same degree forwards. In other specimens of these very 
same species both the sinuations are much less expressed, and again in others the 
striz cross the shell, above and below, almost without any alteration in their course. 
If there are any keels present on the surface of the shell, they necessarily involve 
some kind of change in the direction of the stria. These keels are usually sharper 
in young specimens, and often altogether disappear on the last whorl, or in general 
when they approach the margins of the aperture. 
Supposing, we consider the animal of Strap. pentangulatus similar in form 
to that of the living Solaria, we have then to look upon the insinuation near the 
suture as being produced by the neck of the animal, and the prolongation of 
the outer margin of the aperture by the outer edge of the mantle. When the 
animal has been accustomed, or obliged by circumstances, to carry its shell in a 
more elevated position, which it probably did as long as the shell was of small 
size, the insinuation corresponding to the neck, was made deeper, and certain edges 
or sinuations of the mantle, producing the keels, were bent more externally, and 
consequently these keels were formed more sharply. At the same time, however, 
when the insinuation at the neck was deeper, the peripherical edge adjoining it must 
have become more projecting. Subsequently, when the animal with its shell grew 
to a larger size, it would seem, that its movements became more difficult or legs 
active; the shell, not being so often lifted up and down, was, moreover, carried in 
a more or less horizontal position, the consequence of which would be, that the 
keels and any other insinuations would in the same proportion become less developed. 
* The names Omalaxe, Omalaxon, Omalaxis had scarcely been known, when Deshayes substituted for them 
Bifrontia ; they ought not to be revived again, so as to increase the already existing great confusion. They 
actually never became the property of science, except in a totally misunderstood sense, as commented on by 
Gray or H. and A. Adams. 
aR 
