192 GASTEROPODA OF THE INFERIOR OOLITE. 



Body-whorl short, angular, concave, with a raised rim on the anterior margin, 

 and a wide, depressed base. Aperture quadrate, columella short. In section (fig. 

 1 1) the whorls are subrectangular, and nearly square ; columella and walls equally 

 without folds. Other indications wanting. 



Relations and Distribution. — In comparison with Pachy stylus conicus, Gemm., 

 this species is of somewhat larger habit, and its whorls are not quite so narrow. 

 Coming nearer home one would suspect its relationship to Cerithium Defrancii, 

 Desl. (Mem. Soc. Linn. Norm., vol. vii, p. 193, pi. viii, fig. 36), a fossil occurring 

 in the Bathonian of France. 



Aptyxiella subconica has not hitherto been found out of the Parhinsoni-zone of 

 Aston and Over Harford in the Eastern Cottes wolds. 



Genus — Nerin^a, Def ranee, 1825. 



General definition — " Shell perforate or not ; whorls numerous ; aperture sub- 

 quadrangular, oval or elongate, with a short anterior canal or superficial notch ; lip 

 forming posteriorly a narrow sinus, which leaves in passing off a narrow sutural 

 band ; lines of growth strongly infected near the suture ; columella furnished with 

 folds, which are internally persistent throughout its entire length; other folds appear 

 sometimes on the lip and the columellar side." — Fischer, ' Manuel,' p. 687. 



Before dealing with the question of the sections and subgenera of this most 

 important genus a few remarks on its development in the Jurassics of this country 

 may not be inappropriate. The following passage bearing on this point is quoted 

 from ' Contributions to the Palaeontology of the Yorkshire Oolites.' 1 



" A peculiar interest attaches to the Nerinasas of the Inferior Oolite, since 

 they are the earliest of their kind. The genus, we are told by Sharpe, usually 

 occurs in calcareous strata associated with shallow-water shells. Thus we do not 

 find Nerinseas in the Lias nor in the Striatulus-beds, nor even in the Dogger 

 Sands. Indeed, I am not aware that any remains of the genus have been detected 

 in the lower portions of the Dogger itself, such as the nodule beds which occur at 

 intervals immediately above the Gynocephala-zone (Yellow Sands). But when we 

 come to what was once the more calcareous portion of the Dogger, the shell-bed 

 towards the top is so full of them as to have received the name of Nerinsea-bed. 

 In this bed, only eighteen inches thick, the first noteworthy accumulation of 

 Nerinseas occurs, nor are they ever plentiful again throughout the Yorkshire 

 Oolites until we reach the Corallian Rocks. 



1 ' Geol. Mag.,' decade iii, vol. i, p. 108. 



