342 EOCENE MOLLUSCA. 
tion to which some of the species of this genus have been subject, and the consequent 
uncertainty which attaches to their identification. 
Sandberger has figured and described a British fossil under the above name e/ongatus, 
which, he says, was received from Mr. Edwards, but his figure is rather less elongated 
than are my specimens. 
I have not seen any specimen of Zimnea from the Lower Eocene of England, neither 
have I seen any fossil from either our Upper or Lower Eocene beds that can be referred 
to the genus Physa, though several species of that genus have been figured by 
M. Deshayes from the Paris Basin. 
Fam.—NERITID A. 
Genus 32nd.—Neritina. Lamarck, 1809. 
Generic Character. ‘‘ Testa tenuis, semiglobosa vel ovalis, subtus planulata, non 
umbilicata ; aperturd semi-rotundd ; labro columellari planulato; margine acutiusculo 
subrecto, plerumque denticulato, labro externo intus nec dentato nec crenulato ; operculum 
testaceum semicirculare ; interne appendice laterali instructum.” 
This has been separated from Verita, and intended for those species which inhabit fresh 
water ; but there is little or no difference in the form and general character of the shells of 
the two genera, and most of our present species inhabit waters that are neither salt or 
fresh, as it is to be presumed did their fossil congeners. They can only be distinguished 
under the above respective generic names by the paleontologist, according to the 
indication of habit which at their association with either known marine or estuarine species 
affords, although among living species there are two (JV. viridis and NV. meleagris) which, 
belonging to the section grouped as WVeritine, nevertheless, are found in the sea. 
This diagnosis of WVeritina, as given by Lamarck (fenuis), is not restricted to the 
number of shells that have have been figured and described under this generic name, 
several of them being as thick and ponderous as many of the species called Werita. 
Some are not externally smooth, but are ornamented with ridges and carme ; others have 
denticulations more or less upon the outer and inner lips, while the opercula of Werita 
and WVeritina are thick and possess the same characters alike. M. Deshayes, in the 
second edition of Lamarck’s ‘ Hist. Nat. An. sans Vert.,’ vol. vii, p. 565, has made some 
very just remarks upon the similarity of these genera; and in his last work, ‘ Hist. des 
An. sans Vert. du Bas. de Par.,’ he has grouped all these hitherto called Neriting as 
simply a section of Verifa. As, however, I am describing land and fluviatile shells of 
the older Tertiaries, I have thought it best to retain the name of Weritina for those 
species which, if not restricted to a habitat in fresh water, are met with where the water 
