PULMONATA. 61 
Helicidee, and induced M. de Férussac to arrange the different genera as sub-genera 
merely of the typical genus Helix. 
The present genus, as defined by Lamarck, embraces considerably more than a 
thousand living species; and may well be considered to be “deserving of subdivision, 
were it only to assist the student in the difficult task of investigation.” Very many 
genera and sub-genera (amounting, including the synonyms, to nearly two hundred,) 
have, in fact, been proposed from time to time by different authors; but being 
nearly all founded, more or less, on conchological differences, they are, with few 
exceptions, rejected by the advocates of a strictly natural arrangement. M. Deshayes, 
one of the most able advocates for a system of atfrangement dependent on anatomical 
structure, admits the convenience of having recourse to artificial divisions in this genus 
in which it is impossible to form natural groups; and suggests that the Helices may 
be classed, by the form of the shell, in four sections, consisting of the planorbular 
species, (Zonites, Montfort; Helicella, Lamarck,) the globose species, (4cavus, Montfort, ) 
the carinated species, (Jéerus, Montfort ; Carocolla, Lamarck,) and the trochiform or 
turbiniform species (Pefasia, Beck; Geotrochus, Swain.): and that these sections may 
be again subdivided into groups, according as the species are or are not umbilicated, 
have the aperture simple or reflected, or are or are not furnished with teeth. 
The fossil Helices are more numerous than might be expected with respect to land- 
shells. Many extinct species, from the Freshwater deposits of the Paris basin, 
have been described by MM. Brogniart, (‘Ann. du Mus.’ vol. xv, p. 378,) Deshayes, 
(‘Descr. des Coq. Foss.,’ &c., vol. ii,) Matheron, (Ann. des Sci. et de ’Indust. du 
Midi,’ vol. ii,) Michaud, (‘ Guerin’s Mag. de Zool.,’ 1837,) De Roissy, (‘ Guerin’s Mag. 
de Zool., 1839,’) and Melleville, (( Mém. sur les Sables Tert. Inferieurs du Bassin de 
Paris,’ p. 45;) and from the contemporaneous Freshwater formations in Germany by 
MM. Zeiten, (‘ Petr. Wut., tab. xxix and xxxi,) Steininger, (‘ Bull. Soc. Géol. de 
France,’ vol. vi,) Deshayes, (‘ Ency. Méthod. Vers.,) and Pusch, (‘ Polens. Pal.,’ p. 94.) 
One species only, 1. globosa, has as yet been described from the synchronous deposits 
in England; to this I am enabled to add eight species, one of which is identical with 
an existing species, HZ. Jabyrinthica, Say., found in North America. 
Many species also occur, mixed with marine remains in the Miocene formations of 
Touraine, Dax, and Bordeaux, and in the Pleiocene formations of Piedmont, the Crag 
of England, and its equivalent in Belgium; of these but few are extinct, by far the 
greater number being referred to existing species. 
Among the French species described by M. Deshayes is one (//. dubia), which, on 
the authority of Mr. Underwood, is mentioned as occurring in the Isle of Wight. I 
have not met with any specimen from that place; and M. Deshayes, as I learn from 
that gentleman himself, entertaining doubts as to the English locality, I have not 
considered 7. dudia as an English species. 
