GASTEROPODA PULMONEA. 



349 



We ouR-ht to arrange near them some Helices wliich, without having a douhle-edged cloak, are equally incnpable 

 of retreatitig- within their shell. Hel/.r rufa and hrevipes. Ferns., are examples. 



When the depth of the aperture is greater than its width, as is always the case in shells with an oblong or elon- 

 gated spire, they are the terrestrial Bulhni of Brug., which it appears necessary to subdivide as follows:— The 

 Bidlinu.s; Lam., have an oval rim, thickened in the adult, but without denticulations. In tropical countries, there 

 are some large and beautiful species ; some remarkable for the size of their eggs [equal to that of a Pigeon], and 

 with an equally solid shell ; and others for their reversed shells. In our own country there are several of small or 

 moderate size, and one of them (Helix decoUata, Gm.) has the singular habit of breaking off in succession tlie 

 whorls from its spire. This example has been quoted as a proof that the muscles of the animal can be voluntarily 

 detached from the shell ; for a time does come when this Bulimus preserves no more than a single whorl of all 

 those it possessed at the beginning of the decollation. 



The Pw/*«, Lam., have an obtusely-pointed shell, whose last whorl is narrower than the penultimate, whence 

 it has an elliptical, or sometimes a cylindrical form. The moutli is surrounded by a thickened rim, and en- 

 croached upon, on the side of the spire, by the penultimate whorl. The species are very sntall, living in moist 

 stations, amongst mosses, &c. There is sometimes no toothlet in the aperture, but oftener there is one or more 

 either on the projecting part of the penultimate whorl, or within the outer margin. [The genera Vertigo^ Miill., 

 and Alcea, Jetfreys, appear to have been separated from Pupa on too slight grounds ; for the inferior tuntacula are 

 not absent, as is alleged, but only reduced to a minimum. The Partnia, Fer., deserves probably to be kept dis- 

 tinct ; for the species are ovo-viviparous, while all the others are oviparous.] 



The Chondrus^ Cuv., has, as in these latter PupEe, the mouth of the shell encroached upon by the penultimate 

 whorl, and guarded with plates or toothlets ; but the fig^ure of the shell is more ovate, and more like that of the 

 common Bulimi. Some have the teeth on the rim of the aperture, and others have plaits situated deeper within 

 it. [This genus appears to be synonymous with the Azeca of Leach.] 



Here terminates the section of terrestrial Helices whose shell has a thickened oral rim [or perltreme] in the adult. 



The Siiccinea, Drap., has an ovate shell, with an aperture longer than its width, as in Bulinuis, but larger in 

 proportion ; the outer lip sharp, and the side of the columella almost concave. The Snail is too large to be con- 

 tained in it, and we may almost regard it as a Testacella with a big shell. The inferior tentacula are very small. 

 It lives upon the herbs and the shi-ubs of the brinks of rivulets, \a hence it lias been considered as an amphibious 

 genus. 



We ought to separate from the genus Turbo of LinnEcus, and approximate near the terrestrial 



Helices, the 



Clausilia, Drap., — 



Known by the slender, long, and pointed shell, with the last whorl narrower than the penultimate in 



the adult, compressed, and a little detached. Its mouth is entire and margined, and often toothed or 



furnished with plates. Tlierc is mostly found, 



■witliin the last whorl, a little lamina [commonly 



termed the claus-iam], slightly curved, a little 



like tlie letter S, the use of which to the animal 



is unknown to us.* The species are small, and 



live in moss, at the foot of trees, &e. A great 



number of them are reversed. 



The Achatina, Lam. — 

 Ought likewise to iie separated from the B/'.U(S of 

 Linnaeus, and brought hither. The oval or oli- 

 lung shell has the aperture of Bulimus, but is not 

 margined ; and has the extremity of the colu- 

 mella trmicated, which is the first index of the 

 emarginations we find in so many of the shells 

 of the marine Gasteropodes. These Achatinre 

 arc large Snails wdiieh feed on trees and shrubs 

 in hot climates. t Of such as have, witliin the 

 last Nvhoii, a callus or particular thickening, 

 Montfort makes his genus Liguus. The body- 

 whorl is proportionably naiTow ; and when tlie 

 end of the columella is curved towards the in- 

 the species constitute ^Montfort's Polypheynes 



shells : some Me West Indian, am 

 l;itter, we can only lay ulaim to 

 ciivintrj', llie vi. acicu/u of Lnmarc 



side of 



few European. Ammn; the 

 decidedly a native of lliia 



