362 SPECIES OF THE SYSTEMA. 
the latter appear equally valid; “ pellucida,” indeed, may be 
more critically correct when affirmed of carinatus, yet ‘“sub- 
carinata” seems more suited to marginatus, to which, in truth 
(as Dillwyn has observed), the majority, if not the whole, of the 
cited figures belongs. These display a rather stronger carina- 
tion than is ordinarily to be met with in marginatus, but do not 
at all exhibit that very rapid enlargement of the body whorl 
which is so striking a characteristic in carinatus. Upon the 
whole, then, the ‘Systema’ favours the claims of marginatus ; for 
the expression “pellucida” is only mentioned in the ‘Fauna 
Suecica.’ In other respects the fuller description of that work 
is about equally applicable to either species. It seems likely, 
then, that our author regarded these two allied congeners as the 
same species; indeed, we might reasonably have expected so, 
knowing the greater latitude allowed to specific variation in the 
infancy of conchology. Planorbis having become a generic ap- 
pellation, the probable confusion of species involves no change 
of nomenclature. 
- Belix conwplanata. 
It is not doubted that this shell, whose presence in our 
author’s cabinet has been recorded, belonged to the carinated 
section of the genus Planorbis, of which there are only four mem- 
bers present in the collection of Linneus, to wit, vortex, margt- 
natus, carinatus and nitidus (Rossm. Icon. Conch. pt. 2, pl. 7, 
f.114,115). The first of these can be proved identical with the 
Helix thus named in the ‘Systema;’ “ deorsum carinata”’ dis- 
misses the second, its keel being central. That expression has 
induced certain writers, who erroneously conceived carinatus to 
be the precise equivalent of the H. planorbis, to regard margi- 
natus, so nearly allied to it, but differing in that very feature, as 
the representative of the present shell. But “deorsum carinata” 
is equally applicable to nitidus, whilst ‘‘ supra convexa—sub- 
diaphana— apertura semicordata” (Fauna Suecica) is much 
more critically correct when affirmed of that little shell than of 
its larger rival; and as “ parva admodum” is applied to it in the 
‘Fauna Suecica, in the contrast of its features with those of 
