336 GASTEROPODA OF THE INFERIOR OOLITE. 



anterior extremity of the aperture, thus producing a somewhat Naticoid aspect. It 

 may have been the above peculiarity which induced Phillips to regard this species 

 as a Natica. 



PL XXVIII, figs. 11a, 116. Variety from the Pea-grit of Crickley, almost 

 identical with Nerita ovata, Romer (' Nordd. Oolith.,' p. 156, pi. x, fig. 6). 

 Specimens are a little larger than those from the Dogger, and are somewhat more 

 transversely ovate. The callus on the inner lip is subconvex, thus bringing the 

 shell within the definition of Neridomus. The colour markings, often well 

 preserved, are suggestive of Neritina ; cf. also Neritina Coolcsonii, Desl. 



Relations and Distribution. — In addition to the above a few small shells, about 

 the size of buckshot, occur in the Lincolnshire Limestone both at Weldon and at 

 Ponton, and also more rarely in the Cotteswolds. Because they are small they are 

 sometimes named Nerita " pulla." They are probably micromorphs of N. tumidula, 

 which is the representative on this horizon of N. ovata, Rom., if not absolutely 

 identical. A small species in the Great Oolite of Minchinhampton, described by 

 Morris and Lycett (' Grt. Ool. Moll.,' p. 58, pi. xi, figs. 19, 19 a) as Nerita 

 minuta, Sow., may be ranked in the same category. 



269. Nekita (Neridomus), transverse species. Plate XL, figs. 9 a, 9 b. 



Description : 



Height .... 12*6 mm. 



Width .... 14-3 mm. 



Shell transversely ovate, tumid, moderately thick ; spire low, occupying about 

 one-tenth the height of the entire shell, and formed of about two and a half whorls 

 widely separated by the suture, which is canaliculate at the junction with the 

 body- whorl. This is extremely ventricose, only slightly flattened posteriorly, and 

 sloping. Aperture large, with a thin hemispherical outer lip, whilst there is a very 

 wide and convex (Neridomus) callus on the columellar lip, the margin of which is 

 nearly straight and not denticulated. Colour markings are often well preserved ; 

 these resemble the markings shown on PI .XXVIII, fig. 11a. 



Relations and Distribution. — Throughout the various horizons in the Oolitic 

 rocks we distinguish an ovate and also a transverse form of Nerite. Such a 

 transverse form as the one figured in PI. XL is met with sparingly in the Oolite 

 Marl horizon of the Cotteswolds, and also in the Dogger at Blue Wyke. It is more 

 transverse than Neritina Gooksonii, Desl., yet not precisely like the Nerita trans- 

 versa, von Seebach, of the Upper Oolites. The species is marked in my collection 

 as Neritina " subtransversa." 



