GASTEROPODA. HELICID. 57 
The mantle anteriorly is reflexed, and forms a sort of collar, 
out of which the head passes when the animal is about to move, 
and which closes the aperture of the shell when the animal is 
withdrawn. The foot is separated from the lower part of the 
head by a transverse groove. 
The lateral aperture admits air to the respiratory organs ; it 
contains the anus, and the extremity of the duct from the gland 
which secretes the mucus. This opening is situated on the 
right side in all that are not reversed. 
The tentacula of the Helicide are retractile, and are with- 
drawn, like the finger of a glove inverted, similar to those of the 
Inmacide. The lower ones are almost obsolete in Vertigo. 
All the indigenous species feed on vegetable matter. During 
the winter season they close the aperture of their shell, with 
what is termed an epiphragm (epiphragma), which is for the 
most part membranaceous ; it is however calcareous in Pomatia. 
A similar epiphragm is likewise formed by the young of Tedu 
cingenda during the hotter parts of the summer, as was first 
observed by my friend the Rev. J. Bulwer. 
The nervous system is in all essential points analogous to 
that of the Limacidee, but it is more connected with the mus- 
cles; and the central mass is, in the globose genera at least, 
not placed so near to the inferior ganglion. 
The liver, in all the genera hitherto examined, is quadrilo- 
bate, and these lobes are more or less subdivided into smaller 
lobes. The gall-ducts which arise, each from a peculiar gall- 
bladder, unite into a general tube, which terminates in the an- 
terior extremity of the duodenum. 
STIRS fF. 
Genus 22. SuccINEA. 
Succinea, Draparnaud. 
Testa spiralis; anfractus ultimus maximus. Apertura magna, 
obliqua, posticé ad dextram acuminata. Peritrema nullum. 
Umbilicus nullus. Tentacula breviora: superiora subconica ; 
wnferiora tuberculiformia, brevissima. 
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