NERITA. 335 



Scarborough, and in the Northampton Sand at Duston, thus appearing on two 

 different horizons of the Inferior Oolite. 



The smooth Nerites — Neridomus, Morris and Lycett. 



There is more than ordinary difficulty as regards nomenclature in this group, 

 part of which has originated in the interpretation placed upon that very trouble- 

 some and obscure micromorph, Nerita minuta, Sow. I have endeavoured to focus 

 the smooth Nerites of our Inferior Oolite under two names. There are also a few 

 forms which could not be thus arranged, but as the indications are obscure I have 

 concluded not to attempt them. 



268. Nerita (Neridomus) tomidula, Phillips, 1829. Plate XXVIII, figs. 12 a, 12 6. 



1829 and 1835. Natica tumidula, Phil. Geo!. Yorks., pt. i, pi. xi, fig. 25. (Nerita 



minuta, Min. Conch., pi. cccclxiii?). 

 1854. — — — Morris, Cat., p. 262. 



1884. Nerita minuta, Soto., var. tumidula, Phil. Hudleston, Geol. Mag., 



dec. 3, vol. i, p. 296, 

 pi. ix, figs. 4 a, 4 5, 5 a, 

 51, 6. 



Bibliography, Sfc. — Morris in his Catalogue, it would seem, did not favour the 

 view that " Natica" tumidula, Phil., was to be regarded either as a synonym or 

 variety of Nerita minuta, Sow. On the other hand, the Yorkshire fossil has been 

 labelled Nerita minuta, Sow., in the Lycett collection of the Jermyn Street Museum, 

 presumably in accordance with the identification of Lycett himself. 



Description. — Measurements of a specimen from the Dogger : height 11 mm., 

 width 11 mm. 



Shell ovate, tumid, smooth, and but slightly oblique, the height and width 

 being nearly equal. The spire is composed of a small button-like apex, expanding 

 in the course of two or three widely separated volutions into a large body-whorl, 

 which exhibits a slight posterior flattening, whilst the rest of the whorl is globose, 

 and without ornament other than fine lines of growth. No colour markings are 

 visible in the Dogger shells, the matrix not being favorable. 



Aperture large, outer lip crescent-shaped and thin ; inner lip thick, subconvex, 

 and slightly sinuated, without denticulations on the margin. N.B. — In the 

 majority of specimens, as in the one figured, there is a slight abrasion of the 



