220 GASTEROPODA OF THE INFERIOR OOLITE. 



stone of Swift's Hill and Longridge, and in specimens from the Pea-grit horizon 

 of Longfords (fig. 11 d), which are better preserved than those from Selsley Hill, 

 a third stage is noted. The excavation of the whorls and the sutural prominence 

 disappear, and the whorls become flat or very nearly so. 



The body-whorl is short and angular, with an excavated base ; aperture nearly 

 square, with a short canal. In complete specimens possessing the true body- 

 whorl there are no signs of folds either on the columella or lip. 



The section is very complex ; it has seven folds. Fig. 11 e (Mr. Witchell's 

 type) may be regarded as showing the plan most completely. Fig. 11 c exhibits 

 a somewhat curious divergence. The section of Ptyg. Ojjpelensis differs in no 

 material respect from the sections of Ptyg. bacillus (figs. 5 d and 6 c) already 

 described. The three angles in the head of the anterior columellar fold, mentioned 

 by D'Orbigny as one of the characters of Ptyg. bacillus, are noticeable in 

 Mr. Witchell's specimen, and also in the specimen of Ptygmatis bacillus (fig. 6 c) 

 from the Upper Freestones of Crickley. 



Relations and Distribution. — Ptyg. Oppelensis is a somewhat aberrant member 

 of the bacillus-group. From D'Orbigny 's species it is easily distinguished by the 

 shortness of the whorls, the obtuse-angled subconical spire, and by its marked 

 dimorphism. It has already been indicated in what way it differs from Ptyg. 

 Jonesii. 



The distribution of this species is somewhat local. The Pea-grit of Longfords, 

 the Oolite Marl horizon of Selsley Hill, and, further north, of Swift's Hill and 

 Longridge, are the only localities where it has been identified with certainty. 

 There are so many species which possess this internal structure that strict identi- 

 fication is out of the question without reasonably good specimens. The fossil 

 from the Lincolnshire Limestone of Wakerly (figs. 8 a and 8 b) has already been 

 mentioned in this connection under Ptygmo.tis Jonesii. 



15G. NEEiNiEA [Ptygmatis) producta, Witchell, 1887. Plate XV, figs. 10 a — c. 



1887. JVeeinjea peoducta, Witchell. Vol. cit., p. 34, pi. i, fig. 13. 



Description : 



Spiral angle (regular) . . 3°. 



Height of whorl to width . 1:1. 



Estimated length . . . 150 — 200 mm. 



Shell cylindrical, very narrow. Whorls about twenty-five, flat, sometimes 

 higher than wide, in other cases slightly the reverse ; suture without prominence 

 and close-fitting ; angle oblique. Faint traces of spiral ornament on the early 



