APTYXIELLA. 73 



teriorly, smooth, lip with one fold, columella unknown. There are no longitudinal 

 striae, and in old age the whorls become less concave and are not swollen near the 

 anterior border." From the Cornbrash and Great Oolite of the Boulonnais. 



Description. — In the upper bed of supposed Cornbrash at Akely brickyard are 

 several fragments of a large Nerinxa which seem to belong to this species. They 

 agree with it in general shape, size, and spiral angles, in the concavity and smooth- 

 ness of the whorl surface, in the slope of the sutures, and in the lack of swelling- 

 near the anterior border. There is also one strong fold in the outer lip. 



Nerinaea dimidiata, sp. nov. Plate VII, fig. 10. 



Type. — Length preserved 23 mm. Maximum width 5'5 mm. Spiral angle 10°. 

 Nine whorls are shown. Sutures inclined 75° to axis. Each whorl has the upper 

 part swollen and smooth, the remainder being slightly concave and marked with 

 six equal raised spirals. Interior not seen. The surface of the shell is on the 

 whole step-like. From Scarborough. In the British Museum. 



Here we also see the interior arrangements. The fold on the outer lip is strong 

 and a good deal posterior to the lip on the columella. This latter leaves only a 

 narrow inlet between it and the anterior surface of the whorl — like a canal. On the 

 posterior part of the columella there is in one case a very feeble sign of a third 

 keel (see PI. VII, fig. 16). 



Distribution and Relations. — Three fragments from Akely brickyard are all that 

 have been seen. They are associated with Anabacia and Avicula braamburiensis. 

 It is probable that a similar occurrence in the continuation of this bed past Newport 

 Pagnell has caused the record of N. goodhalli (Sow.) at Gayhurst. There is a 

 considerable resemblance between the tAvo, but our species has not the swelling 

 noticeable in the anterior part of the whorl, nor the long fold on the posterior wall 

 in the whorl of the latter species. The first distinction separates it also from 

 N. desvoidyi, D'Orb., which exhibits different relative positions of the two principal 

 folds ; but our species is no doubt related to both these Corallian forms by way of 

 ancestry. 



Genus APTYXIELLA, Fischer. 



Aptyxis, Zittel, name pre-occupied and altered to Aptyxiella by Fischer (' Man. 

 de Conchyl.'). Zittel' s diagnosis is as follows: "Turreted, very slender, imper- 

 forate, aperture quadrangular, inner and outer lips without folds, columella some- 

 what thickened." This name may be used for all shells with anterior canals whose 

 external shape suggests a Nerinsea, but whose internal section shows no folds. 



10 



