70 EOCENE MOLLUSCA. 
With them are numerous specimens of a species of Hydrobia, from which I should 
imagine it to be an estuary species. ‘The exterior is covered with exceedingly fine striae, 
those on the siphonal region being rather larger and more distant, and the pedal side of 
the ventral margin is slightly contracted, giving a gentle curvature to the base. The 
hinge-line is straight, and extends half the length of the shell. The pedal region occu- 
pies about one fifth of the specimen. 
13. Moprota prema, S. Wood. Pl. XIII, fig. 4, a, 6. 
Spec Char. M. testa minutd, oblongo-ellipticd, tenuissimd, tumidd, striatd, striis in 
medio interruptis ; pedi-regione parvd, subacutd, angustiore ; margine dorsali subangulata ; 
nmargine ventrali subrectd. 
Shell minute, elliptically oblong, very thin, tumid, striated, with a small, naked space 
in the ventral region ; pedal region small, pointed; dorsal margin obtusely angulated ;— 
ventral margin nearly straight. 
Length, {th of an inch. 
Locality. Barton (Hdwards). 
This small and elegant little shell differs from JZ. evimia in the outline, and also in the 
striation. The exterior is covered with striae, except on a small space of the ventral region, 
which is naked. The contour of this species is less rounded than that of caimia, and the 
striae are fewer and broader. The dorsal edge is covered with crenulations, like those on 
the so-called A/odiolarca, but these are merely extensions of the prominent rays which 
project at the margin. 
14. Moprota semi-nupA, Deshayes. Tab. XIII, fig. 1, a, 6. 
MoproLa spMI-NuDA. Desh. Coq. Foss. des Env. de Par., t. i, p. 264, pl. 39, figs. 20—22. 
— — Morris. Catal. Brit. Foss., p. 211, 1854. 
— — Desh. An. sans Vert. du Bassin de Par., t. ii, p. 12, 1860. 
Myvitus spmi-Nupus. Desh. Ency. Méth. Vers., t. ii, p. 569, No. 36, 1850. 
— _ D’Orbigny. Prod. de Paléont., t. ii, p. 424, No. 1634, 1850. 
Spec. Char. M. testé ovato-ellipticd, cordatd, tumidd, tenuissimd, fragili, striata ; 
striis exilissimis ornatd ; spatio submediano levigato ; umbonibus minimis, depressis, sub- 
terminalibus. 
Shell ovately elliptical, heart-shaped, inflated, very thin and fragile, ornamented with 
very fine strize ; centre portion plain, or free from radiating ridges; umbones small, de- 
pressed, and nearly terminal. 
Length, $ths of an inch ; hezghé, 4 an inch. 
Localities. Barton (2dwards). 
France, Senlis, Grignon (Deshayes). 
