76 CRETACHOUS GASTROPODA 
Deshayes very properly observes (vide Anim. s. vert. bas. de Paris, III, p. 541) to 
those species only which have the margin of the outer lip not thickened, while for 
those forms which have a thickened outer lip, like Marginelia and others, but only 
a few anterior plaits on the columella, Hinds’ name Volvarina could remain in use. 
Gray (Guide, 1857, p. 30) retains Volvaria mm the same sense, and does not 
acknowledge any living representative of the genus, while Deshayes knows two 
living species, one of which is the Volvaria pallida. It cannot be questioned that, 
as regards the general form of the shell, the fossil genera Acteonella, Volvulina, 
Cylindrites and others show the greatest relation to Volvaria and Volvarina; there 
are, however, some very important reasons, which urge the classification of these 
fossils in the group OprsrHoBRancuta. We have already (page 58) referred to 
Hrato, Risso, advocating the view of its belonging to the Crpraipxz. Pachybathron, 
Gask. appears to be more successfully classed by Gray and Chenu in the family 
CASSIDID&. 
As I have already stated, Deshayes is determined, after a repeated and minute 
exanination of the forms of all the az1rerveziry~, to class this group of shells with 
the Cyprazips. Deshayes proposes this, I believe, only on the ground of the 
external similarity of the animals in preference to all other distinctions. Let us 
consider the animal first: In Marginella (restricted) the animal has long tentacles, and 
an expanded mantle, enveloping the shell as in all other Crrraz~, but the mantle 
is quite as much expanded in the true Vozurrp also (as for instance in several of the 
species of Melo and Scapha); it is, however, always smooth on the exterior surface, 
and not provided with those filamentous appendices, which are very characteristic 
for by far the greatest number of the Crrrazips. If the length of the tentacles 
(and they are not so very long in several other true Marginelle) ought to be taken 
as a conclusive distinction, how is it possible for Deshayes to maintain the unity 
of the genus Marginella, and not to separate even generically Persicula, the animals 
of which are decidedly more like rozvrmvz than crprarvz/ Looking further to 
the dentition of the radula, we find no support whatever for such a transfer of 
Marginella to the Crpraipm. The shell of Marginella, which has columeliar plaits 
during all stages of growth, is by this character alone decidedly more nearly related to 
the Voxturrm-» than to the Crrram, in which the dentition of the margins appears 
only in stages of maturity. Besides this, the outer lip In many m4remELtiIne 
has only a thickened and shelving outer edge and is not involute, as, without 
exception, it is in the Crrra#ipz. 
Not many fossil species of the Marginelline are known. They appear to have 
been more numerous in the eocene period than in the neogene, but none are as 
yet known from the cretaceous strata. The single species Marginella inwoluta, 
Zekeli,* from the Alpine Gosau deposits has been shown to be a Cyprea, or at 
least to belong undoubtedly to the sub-family crprzrvz.t 
* Abh. Geol. Reichs Anst. Wien, 1852, I, p. 65, Pl. IX, Fig. 11. 
+ Sitzh. Akad. Wien, 1865, Bd. LIT. Revision ete. p. 64. 
