332 GASTEROPODA OF THE INFERIOR OOLITE. 
Genus—Nerita, Linnews, 1758. 
Systematic conchologists, such as Fischer, do not carry the genus Nerita so far 
back in time as the Jurassic period. That author (‘ Manuel,’ p. 800) observes that 
the Jurassic forms of Nevita are doubtful and belong to the genus Neridomus, Morris 
and Lycett. Accepting provisionally the classification of these authors for the 
Neritoid shells of the Lower Oolites, [think that Nevita will cover the more rugose 
and costated forms with flattened inner lip, though, as far as my experience goes, 
there is no denticulation of the edge. Viewing Neridomus as a section of Nerita, 
this will include shells which are smooth and have the inner lip convex. It has 
always seemed to me that Neridomus was more nearly related to Neritina than to 
Nevita. Cossmann, I may remark, is disposed to query the value of the generic 
distinction between Neritina and Nerita, and he has no hesitation in placing all the 
Nerite-like shells of the Jurassic rocks under Nevita.’ 
As a matter of fact, I distinguish in our Inferior Oolite three rugose and costated 
forms, which no doubt are closely related, and more or less run into each other. 
There are also two, if not three, fairly distinct smooth forms which belong to the 
section Neridomus, besides some others which are too obscure to notice. 
265. Nerita costutata, Deshayes, 1838. Plate XL, figs. 6a, 6b; and ?P Plate 
XXVIII, figs. 6a, 6b. 
1824. Nerira costata, Sowerby. Min. Conch., pl. cecelxiii, figs. 5 and 6. 
1838. —  cosrunata, Deshayes. Lamarck, Anim. sans Vert., 2nd edit., 
vol. viii, p. 617. 
1851. — — _ Morris and Lycett, Great Ool. Moll., pt. 1, 
p- 57, pl. viii, fig. 6. 
1884.P — — — [var.] Hudleston. Geol. Mag., dec. 3, vol. i, 
p- 299, pl. ix, fig. 10. 
1885. —  minura, Sow. Cossmann, Et. Bath., p. 154, pl. xiii, figs. 30, 31. 
Bibliography, §c.—There has been much trouble in regard to the synonymy of 
this well-marked species, first described by Sowerby from the Great Oolite of 
Ancliff. But it seems to me that this confusion has been intensified through the 
view taken by d’Orbigny in the ‘ Terrains Jurassiques’ (vol. ii, p. 231) that 
Nerita minuta, Sow., is the young stage of the costate species. I quite agree that 
Morris and Lycett were not correct in their identification of Sowerby’s Nerita 
1 «Fitage Bathonien,’ p. 151. 
