202 GASTEROPODA OF THE INFERIOR OOLITE. 
Relations and Distribution—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. attenuata. 
In view of the undoubted fact that forms of Nerinea 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 Nerinzeas 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. Nerina DEDUCTA, sp. nov. Plate XIII, fig. 8 
Description : 
Spiral angle . : : ste Ore 
Height of whorl to with : : gos 
Approximate length . : : . 80mm. 
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 whorls 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-group 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-group, from which it is distinguished by its smaller spiral angle and more 
cylindrical figure. Not abundant. 
