202 GASTEROPODA OF THE INFERIOR OOLITE. 



Relations and Distributiorb. — These shells are found at one or two points in 

 the Lincolnshire Limestone, and notably at Wakerly and Nettleham. Such speci- 

 mens as fig. 6, from the Oolite Marl, seem to constitute a connecting link both 

 with N. oolitica and N. oMenuata. 



In view of the undoubted fact that forms of Nerinaea do run into one another 

 by easy gradations, some might prefer to regard N. parva, oolitica, attenuata, and 

 expansa as varieties of one species ; but if we accept this lumping view, it would 

 be scarcely possible to constitute any species for triplicate Neringeas with little or 

 no ornament, as the similarities might be extended indefinitely. A form (PL XIV, 

 fig. 6) which is not uncommon in the upper beds of the Lincolnshire Limestone 

 at Great Ponton may be a narrow variety of this species. The chief difference 

 appears to be that the columella is partly hollow. There are also some trifling 

 differences in the section. 



134. Neein^a deduota, sp. nov. Plate XIII, fig. 8. 



Description : 



Spiral angle . . . . .6°. 



Height of whorl to width . . . 1 : 1*35. 



Approximate length . . . .80 mm. 



Shell subcylindrical, spire dimorphous. For about one-third the distance from 

 the apex the sutural belts are very thick and prominent, with corresponding 

 excavation of the whorls. From twelve to fourteen wliorls present this phase. 

 The change to a plain and flat whorl is rather sudden; there are about ten of 

 these, fitting close so as to produce a very elongated cone. In the specimen 

 figured the slightly raised rim on the posterior margin of each whorl is well 

 preserved. No ornaments in the anterior whorls other than lines of growth, 

 which seem to have been nearly straight. 



Body- whorl not prominent, smooth, scarcely excavated ; aperture oblong, with 

 rather a wide and relatively long canal. Section triplicate, and closely resembling 

 that of the oolitica- growp generally. 



Relations and Distribution. — As this form occurs in the Pea-grit horizon, it may 

 be regarded, in a certain sense, as the precursor of the several forms of the 

 oolitica-gvoViY), from which it is distinguished by its smaller spiral angle and more 

 cylindrical figure. Not abundant. 



