70 EOCENE MOLLUSCA. 



With them arc numerous specimens of a species of Hgdrobia, 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. Modiola pygmjEa, S. Wood. PL XIII, fig. 4, a, b. 



Spec Char. M. testa minutd, oblongo-ellipticd, tenuissimd, tumidd, striata, striis in 

 medio interruptis ; pedi-regione parvd, subacutd, angustiore ; margine dorsali subangidatd : 

 margine 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, ~Sk\ of an inch. 



Locality. Barton {Edwards). 



This small and elegant little shell differs from M. eximia 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 eximia, and the 

 striae are fewer and broader. The dorsal edge is covered with crenulations, like those on 

 the so-called Modiolarca, but these are merely extensions of the prominent rays which 

 project at the margin. 



14. Modiola semi-nuda, Deshages. Tab. XIII, fig. 1, a, b. 



Modiola semi-nuda. Desk. Coq. Foss. des Env. de Par., t. i, p. 264, pi. 39, figs. 20 — 22. 



— — Morris. Catal. Brit. Foss., p. 211, 1854. 



— — Desk. An. sans Vert, du Bassin de Par., t. ii, p. 12, 1860. 

 Mytilus semi-nudus. Desk. Eucy. Meth. Vers., t. ii, p. 569, No. 36, 1850. 



— — VOrbigny. Prod, de Paleont., t. ii, p. 424, No. 1634, 1850. 



Spec. Char. M. testa ovato-ellipticd, cor data, tumidd, tenuissimd, fragili, striata; 

 striis eceilissimis ornatd ; spatio submediano Javigato ; umbonibus minimis, depressis, sub- 

 terminalibus. 



Shell ovately elliptical, heart-shaped, inflated, very thin and fragile, ornamented with 

 very fine stria? ; centre portion plain, or free from radiating ridges ; umbones small, de- 

 pressed, and nearly terminal. 



Length, |ths of an inch ; height, \ an inch. 



Localities. Barton {Edioards). 



France, Senlis, Grignon {Deshages). 



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