346 EOCENE MOLLUSCA. 
No. 268. Neritina concava, J. Sowerby. Tab. XXXIV, fig. 14 a—e. 
Neritina concava, J. Sow. Min. Conch., tab. ecelxxxv, figs. 1—8, 1823. 
_ — Desh. (2nd edit. Lamk.). An. 8s. Vert., t. vili, p. 597, 1838. 
— _ Morris. Catal. Brit. Foss., 2nd edit., p. 264, 1854. 
— = J. Lowry. Chart Brit. Tert. Foss., pl. iii, 1866. 
_ — Lyell. Students’ Elemts. of Geol., p. 231, 1871. 
- — Sandberg. Wand- und Siissw.-Conch., p. 267, tab. xv, fig. 13, 1872. 
NERIvTA — Nyst. Coq. foss. de Belg., p. 436, pl. xxxvii, fig. 30, 1843. 
Spec. Char. N. Testé ovato-globosd, levigatd, apice obtuso; lineolis fuscis parallelis 
vel reticulatis tenuissimis ornaté; anfractibus supra concavis ; apertura semicirculart ; 
columellé arcuatd, in medio tenuiter denticulatd. 
Diameter, 2ths of an inch. 
Localities. Hempstead (Morris), Headon Hill, Muddiford (S. Wood). 
Belgium: Kleyn-Spauwen (/Vys/). 
This species is abundant at Headon Hill, and the operculum also is sometimes found, 
a figure of which I have given. This operculum is flat on the exterior, and has not the 
curvilinear depression possessed by that of WV. Forbest?. ‘The projecting prominent teeth 
on the inside appear also to be different from that on the operculum of Fordesii, the 
two bifurcations of the denticle being unequal in size, and expanding more widely. The 
outer lip of our shell is plain and sharp, the inner moderately extended; and the 
columella is sharp-edged and slightly concave, and has upon its centre about half a dozen 
fine denticles. These shells are variously ornamented on the exterior, generally having 
fine cancellated openings, produced by lines of oblique brownish colouring matter, 
crossed by similar oblique lines which together form small, lozenge-shaped, white spaces, 
but the lines are sometimes confluent. 
This species is not mentioned as a fossil of the Paris Basin, but the shell from Kleyn 
Spauwen, as given by M. Nyst, appears to be identical with it, and that author has 
given as a synonym of it JV. picta, of Dubois, from Volhynia, though with a doubt. In 
the description of Dubois’ species, however, the words “ columella unidentata”’ occur, a 
character which our species does not possess. 
Mr. Whitaker, in his ‘Memoir, at p. 579, has introduced concava as from the 
Woolwich beds at Charlton, but this I have not been able to verify, and I conclude that 
it was inserted on the authority of the reference by J. Sowerby in ‘ Min. Con..,’ tab. 385, 
of that shell to Charlton, an erroneous reference, as poimted out by Mr. Prestwich in 
‘Quart. Journ. Geol. Soe.,’ vol. x, p. 121. Mr. Sowerby also in the same table represents 
a specimen said to be from Highgate, but it does not look like our own shell, as the 
volutions (which in that figure are sinistral) do not exhibit that concave depression on 
their upper part which is peculiar to this species, and from which its name was, I 
presume, given. Some specimens have a white spiral band, like that upon JV. ornata. 
