118 



NERITINA concava. 

 TAB. CCCLXXXY. —Figs. 1 to 8. 

 Spec. Char. Obovate, with a prominent obtuse: 

 spire; upper part of each whorl concave^ 

 aperture semicircular ; lip entire. 



J- HE surface of this Neritina is elegantly marked with 

 fine zizaghnes 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 ofpreservation. 

 The operculum is not known. 



I— 11^ 

 NERITINA uniplicata. 

 TAB. CCCLXXXV.— i^^^r^. 9 and 10. 



Spec. Char. Subglobose, with a concealed 

 spire, and one plait upon the rather convex 

 columella lip. 



^o variety of colour decorates this plain looking shell; 

 the apex of the spire is indicated, in specimens tiiat are 

 not worn, only by a sunk |)oint, irom 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 Flumstead, and near 

 New Cross, on the banks of the Canal above the London 

 Clay. 



• This species has a kind ci' chamber in it discoverable by removing 

 the end of the spire, that does not occur in the fossil, or any other recent 

 one that I have opened. 



