10 PULMONATA. 
(Limneidee) occur in the English Wealden, but fossil land-snails 
have not been found in strata older than the tertiary in Europe, 
and then under forms generically, and even in one instance spe- 
cifically, identical with living types of the New World (Mega- 
spira, Proserpina, Glandina,and Helix labyrinthica).— Woodward. 
The oldest American fossils of this subclass occur in the 
Carboniferous. 
The lingual dentition of the Pulmonata confirms, in a remark- 
able manner, those views respecting the affinities of the subclass, 
and its zoological value, which have been deduced from the more 
obvious characters afforded by the animal and shell. They have, 
without known exception, rows of very numerous, similar teeth, 
with broad bases, resembling tessellated pavement. Their crowns 
are recurved,and either aculeate or dentated. The lingual ribbon 
is very broad, often nearly as wide as it is long; and the number of 
teeth in a row (though usually a third less) is sometimes as great, 
or even greater, than the number of rows. The rows of teeth are 
straight or curved or angulated ; when the rows are straight the 
teeth are similar in shape; curves indicate gradual changes, and 
angles accompany sudden alterations of form.— Woodward. 
The jaw is single, or is composed of three pieces, never of two 
pieces as in the branchiferous snails. 
In the young snails the temporary vellum is rudimentary or 
absent, with the exception of the maritime genera, in which it is 
well-developed. The first development of the shell, at least in 
Limax, Clausilia and Helix, is within, instead of on the exterior 
surface of the mantle as in the other gastropods. It is similar 
in most cephalopods, but in these the shell continues internal, 
whilst in most of the pulmoniferous genera it becomes external 
at an early period. 
The Pulmonata are conveniently divided into the orders :— 
1. SryLoMMATOPHORA (Geophila, Ads. Nephropneusta, [her- 
ing).— Kyes at the ends of the superior tentacles. 
2. BasoMMATOPHORA (Branchiopneusta, Lhering .—Eyes at the 
base of the tentacles. 
Orver STYLOMMATOPHORA. 
Terrestrial mollusks having four tentacles, the superior pair 
invaginate or retractile, oculiferous at their extremities. They 
may be divided into Monotremata and Ditremata, according to 
the union or separation of the sexual openings. 
Suporper MONOTRE MATA. 
Male and female orifices united ; oculiferous tentacles invertible. 
* Agnatha. Mouth without jaw; generally no median tooth 
in the radula; lips often developed into feeler-like appendages ; 
neck commonly elongated, and peculiarly furrowed on the back. 
