200 GASTEROPODA OF THE INFERIOR OOLITE. 



smooth, and the increase by steps less pronounced. The point where this change 

 comes on varies in individual shells. 



Body- whorl angular, smooth, and slightly projecting; aperture oblong, with 

 rather a wide and moderately reflexed canal. Section triplicate ; one acute fold 

 near the centre of the outer wall, one rather wide shallow fold low down in the 

 columella, one acute small fold in the posterior wall. 



Belations and Distributiofi. — This species is essentially the common triplicate 

 Nerinsea of the Oolite Marl horizon, and probably passes by gradations into Nerinsea 

 attenuata on one side, and Nerinsea expansa on the other. Figs. 4 a and 4 b may 

 be regarded as typical ; figs. 6 and 7 seem to connect it with Nerinsea expansa of 

 the Lincolnshire Limestone. 



The chief localities are Swift's Hill and Longridge in the Cotteswolds, and 

 similar forms may be traced in parts of the Lincolnshire Limestone. It is some- 

 what singular that so abundant a species should have escaped the notice of Lycett ; 

 but most species, eveu the commonest, are wont to be local in distribution. 



131. NBEiNiEA LoNGPOEDBNSis, sp. nov. Plate XIII, fig. 5. 



Description : 



Spiral angle (obtuse) . . . .10°. 



Height of whorl to width . . . 1 : 1'4. 



Length . . . . .90 mm. 



Shell cylindro-conical, turrited. Whorls about sixteen. The apical whorls, 

 as in N. ooUtica, are thickened at the suture, though scarcely to the same extent. 

 The whorls are much excavated, and this is continued throughout, the more 

 mature whorls being much pinched in about two-thirds down, which gives this 

 part of the spire a peculiarly constricted look. 



The aperture is oblong, and the section is remarkable for the smallness of 

 the folds. 



Belations and Distribution. — The pinching in of the outer portion of the 

 whorls gives this genus a superficial resemblance to N. cingenda, Phil. Rare in 

 the Upper Pisolite of Longfords. 



