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EOCENE MOLLUSCA. 



less of the original colour remaining upon them ; but those I have from Milford, which 

 appear to be of the same species, though rather larger, are destitute of colour or markings 

 of any kind. The upper part of the outer lip is generally, though not always, slightly 

 elevated above the vertex, and somewhat thickened within, at some distance from the 

 edge. The inner lip is thick and flattened, with a sharp edge to the columella, which 

 has a few denticles in the centre and a distinct tooth at the upper part. 



This species seems to partake of the characters by which the genus Nerita is 

 distinguished as well as of those of the genus Neritina, in which I have placed it. 



No. 271. Neritina Eorbesii, 8. Wood. Tab. XXXIV, fig. 16 a—c. 



Spec. Char. N. Testa ovato -oblong a, laevigata, tenuissime lineolatd vel ornatd ; 

 spird depressd ; anfractibus rapide crescentibus, aperturd semilunari expansd ; area 

 columellari lata, plana, in medio tenuissime denticulatd ; labro acuto simplici. 



Diameter, fths of an inch. 



Locality. Headon Hill (S. Wood). 



This is equally abundant with N. aperta, and I have separated it in consequence of 

 its difference in form. Our present shell is narrower ; that is to say, it has a more 

 extended outer lip, the aperture being wider or more expanded from the inner lip to the 

 outer than in the preceding species. The apex is also much depressed, and the upper 

 part of the shell is nearly flat, with spire indicated by a narrow depressed suture. The 

 coloured markings are various. 



I have obtained several specimens of this species with its operculum in position, and 

 this adjunct I have had figured. The inner side of the operculum is furnished with a 

 prominent projection at the lower part, which is bifid or forked, expanding at an angle of 

 about 45°. The outer side of this operculum shows a curvilinear depression with a 

 corresponding elevation on the inner surface. N. Forbesii much resembles N.fiuviatilis, 

 but that shell has a more elevated spire. It does not differ greatly from N. transversa, 

 Ziegler, figured by Rossinasler, 'Icon.,' pi. vii, fig. 121, but I have not specimens of 

 that species with which to compare it. 



No. 272. Neritina zonula, 8. Wood. Tab. XXXIV, fig. 19. 



Spec. Char. N. Testa rotundato-ovatd, lavigatd ; vertice depresso ; anfractibus con- 

 vexiusculis, zonulatis aut parum angulatis, superne concavis ; lineolis fuscis parallelis 



