﻿PROSOBRANCHIATA. 



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No. 269. Neritina tristis, Forbes. Tab. XXXIV, fig. 12 a, b. 



Nerittna trtstis, Forbes. Mem. Geol. Surv. Isle of Wight, p. 46, 1856. 

 — — J. W. Lowry. Chart Brit. Foss., pi. ii, 1866. 



Spec. Char. N. Testa fused, ovato-obtongd, tenui, spird brevi, obtusd, anfractibus 

 tribus, ultimo magno, aperturd magna semilunari, columella plana margine simplici, labro 

 aculo, edentulo. 



Diameter, -j^-ths of an inch. 



Locality. Hempstead {Forbes). 



A few specimens were many years ago given to me by the late Edward Forbes with 

 the above specific name attached. These appear to differ from N. concava in having a 

 rather less elevated spire and a slight depression round the upper part of the volution, 

 as in concava ; but I can discover no angularity in the volutions. It is of a uniform 

 sombre or brownish colour, from which I presume it received its name. This has not 

 been figured in the ' Geol. Survey Memoir,' but it is very well represented by Mr. 

 Lowry in his { Illustrations of British Fossils ' above referred to. Forbes described it 

 (' Memoir Geol. Survey,' p. 46) as " a small globose shell, with volutions rather angulated ; 

 aperture semilunate, inner lip obscurely denticulated, surface smooth without ornamen- 

 tation." 



No. 270. Neritina aperta, /. Sowerbg. Tab. XXXIV, fig. 20 «, b. 



Nerita aperta, J. Sow. Min. Conch., t. ccccxxiv, figs. 2, 3, 4, 1823. 



_ _ Morris. Catal. Brit. Foss., 2nd edit., p. 264, 1854. 



— — J. Lowry. Chart Brit. Tert. Foss., pi. iii, 1866. 

 Neritina (Mitrula) aperta, Sandb. Land- nnd Sussw. -Conch., p. 269, t. xv, figs. 



15, 15 a, 1872. 



Spec. Char. N. Testa subglobosd, apice depresso, vix conspicuo ; anfractibus 2 — 3 ; 

 lineis tenuibus ornatd ; aperturd semilunari ; margine dextro, acuto ; columella plana, 

 margine acuto, in medio minute denticulatd, posteriore unidentatd. 



Height, \ of an inch ; diameter, i^ 6 -ths of an inch. 



Localities. Colwell Bay (.7. Sowerbg), Headon Hill, Milford {S. Wood). 



The shell figured by Sowerby as above referred to is a good representation of a small 

 specimen of this species, which is not rare in the Upper Eocene of Hampshire and the 

 Isle of Wight. I have not, however, seen any so small as those represented in figures 3 

 and 4 of tab. 424 of ' Min. Condi.,' which, no doubt, were immature specimens. The 

 ornamentation is variable, as pointed out by Mr. Sowerby, and the shells have more or 



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