NERITA. 333 



minuta, as pointed out by Cossmann {loc. cit.), but that is a very different thing from 

 our accepting the view that Nerita minuta and Nerita costata are different stages of 

 the same species. The figures of d'Orbigny are altogether beside the mark, as 

 his artist evidently had no idea whatever of Nerita costata. Specimens from the 

 Pea-grit, except as to size, very much resemble the Ancliff fossil, and we can trace 

 the costate form in the very earliest whorls. Consequently, as far as the Inferior 

 Oolite is concerned, I cannot agree to the union of these two species of Sowerby, 

 and must continue to regard Nerita minuta as a distinct fossil. The Nerita minuta 

 figured by Cossmann is evidently Sowerby's Nerita costata = costulata, Deshayes. 



Description : 



Height .... average 9 mm. 



Width ..... 11—12 mm. 



Shell transversely ovate, tumid, moderately thick ; variable in size, but rarely 

 exceeding 15 mm. in width. Spire small and depressed, consisting of about two 

 and a half whorls, which are costated and sunk in a deep sutural channel. Body- 

 whorl relatively large, constituting about nine-tenths of the total height, and 

 flattened posteriorly so as to impart a certain degree of angularity to the shell, which 

 is ornamented throughout with numerous and rather fine radial costae, closely set 

 and deflected posteriorly. Aperture large ; columellar lip wide and flat, but without 

 denticulation of the inner margin. 



Relations and Distribution. — This species may be regarded as one of the most 

 typical Nerites occurring in the Lower Oolites. The most numerous and best 

 preserved specimens occur in the Pea-grit of Crickley Hill, where they are seen to 

 differ somewhat in shape ; here and there a specimen being unusually transverse, 

 as though approaching the contour of Nerita Buvignieri of the Great Oolite. The 

 shorter specimens exhibit a tendency to merge into the species next described. In 

 the Yorkshire beds Nerita costulata is rare, being generally represented in the 

 Dogger by Nerita pseudo-costa (perhaps only a variety), whilst in the Scarborough 

 Limestone it seems to pass into a more rugose form. 



266. Nerita pseddo-costata, d'Orbigny, 1850. Plate XXVIII, figs. 7, 8, and 9. 



1829 and 1835. Nerita costata, Sow., sp. Phillips, Geol. Yorks., pt. 1, pi. xi, fig. 32. 



1850. — pseudo-costata, d'Orl. Prod., i, p. 264 (non Gmelin, 1789). 



Blue Wick. 

 1854. — — — Morris, Cat., p. 264. Blue Wick. 



1884. — — — Hudleston, Geol. Mag., dec. 3, vol. i, 



p. 298, pi. ix, figs. 7, 8, and 9. 

 Cf. also — costifeea, Piette. Cossmann, fit. Bath., p. 156, pi. xvii, figs. 59 



and 60. 



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