332 EOCENE MOLLUSCA. 
Fam.—CYCLOPHORID Ai. 
Genus 28th—Cyrctostoma. Lamarck, 1799. 
Generic character. ‘Shell turbinated, thin ; axis perforated, aperture oval, peristome 
continuous, simple or expanded, epidermis thin, operculum shelly paucispiral.” 
A large group of land shells have been described under the above generic name, 
which seem to have only one character in common, viz. a circular mouth, with a thickened, 
expanded, or reflected peritreme, the shells themselves being some of them nearly 
cylindrical like C. fanulum, or discoidal like C. planorbulum ; and they have in conse- 
quence been separated into numerous proposed genera, depending for those divisions 
principally, if not entirely, upon the differences in the angle of volution. 
Two species from our Eocene deposit at Sconce have been described by Mr. Edwards 
under one of these divisions, called Cyc/otus, with a depressedly conical form (see his 
remarks on the Genus, p. 116 of his work). 
No. 254. Cyctostoma ? Mumia, Lamarck. Tab. XXXIV, fig. 2 a—d. 
CycLostoma MuMIA, Lamk. An. du Mus., t. viii, pl. xxxvii, fig. 1 a, 6, 1806. 
— — Desh. Coq. foss. des Env. de Par., p. 76, pl. vii, figs. 1, 2, 1824. 
_- — Id. An. sans Vert. du Bas. de Par., tom. ii, p. 882, 1858. 
— — Forbes. Mem. Geol. Surv. Isle of Wight, p. 68, 1856. 
—_— —- Morris. Catal. Brit. Foss., 2nd edit., p. 244, 1854. 
—- — J.W. Lowry. Chart Brit. Tert. Foss., pl. ii, 1866. 
MeGaLomastoma Mumia. Sandberger. Land- und Siissw.-Conch., p. 217, t. ii, fig. 
20, and t. xv, fig. 16 a—e, 1872. 
Spec. Char. (C. “ Testé cylindraceo-conicd, transversim striatd, striis longitudinalibus 
subtillissimis ; apertura oblique ovata ; labro crasso.’—Desh. 
Length, \ inch; breadth, 3ths of an inch. 
Locality. Brading Harbour, Forbes. Sconce, Ldwards. 
France, Grignon and numerous other Upper Eocene localities. 
This fossil is said to be abundant in some of the numerous localities given for it in 
the Upper Eocene beds of France. It is at Grignon in association with many marie 
shells, and it appears to be there of larger dimensions than our own specimens. It has 
long been known, and its habits have been frequently a subject of discussion from its 
occurrence with a marine fauna. In this country specimens ‘are not abundant, and all 
that I have seen are casts. M. Deshayes describes five distinct varieties : 
