JIB 
NER1TINA concava. 
TAB. CCCLXXXV. — Figs. 1 to 8 . 
Spec. Char. Obovate, with a prominent obtuse: 
spire; upper part of each whorl concave 
aperture semicircular ; lip entire. 
T he surface of this Neritina is elegantly marked with 
fine zizag lines of a dark colour, that undulate so deeply 
as to touch each other at their angles, and thus form the 
resemblance of a net ; the aperture is smaller, and the 
columella lip less flattened and blunter than in N. fluvia- 
tilis, the common recent English species, which it has 
often been taken for;* its markings are also generally 
much more minute. 
A very abundant shell in some parts of the so called 
upper Marine Stratum of the Isle of Wight; it also oc- 
curs at Muddiford, whence the variety fig. 2. was sent 
me by Miss Beminster. Fig. 5. represents a mutilated 
specimen found at Highgate, and fig. 8. is remarkable 
for shewing two kinds of marking upon the same shell. 
This species also occurs at Charlton, with the follow- 
ing, but rarely, and always in a bad state of preservation. 
The operculum is not known. 
NERITINA uniplicata. 
TAB. CCCLXXXV. — Figs. 9 and 10. 
Spec. Char. Subglobose, with a concealed 
spire, and one plait upon the rather convex 
columella lip. 
IN o variety of colour decorates this plain looking shell ; 
the apex of the spire is indicated, in specimens that are 
not worn, only by a sunk point, from which a single curve 
runs to the aperture : worn individuals shew the turns of 
the spire ; portions of the epidermis remain sometimes 
of an olive green colour. 
Found abundantly in the uppermost stratum of gravel 
holding shells, above the bed of sand, between Charlton 
and Woolwich, accompanied by Melanopsides, Cyclades 
Ostreae, &c. being a mixture of marine and freshwater 
shells : it is also to be met with at Plumstead, and near 
New Cross, on the banks of the Canal above the London 
Clay. 
* This species has a kind of chamber in it discoverable by removing 
the end of the spire, that doe* not occur in the fossil, or any other recent 
one that I have opened. 
