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. 11e (Mr. Witchell’s 
type) may be regarded as showing the plan most completely. Fig. 11 ¢ exhibits 
a somewhat curious divergence. The section of Ptyg. Oppelensis differs in no 
material respect from the sections of Ptyg. bacillus (figs. 56 and 6¢) 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. 
Jonesit. 
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. 8a and 8b) has already been 
mentioned in this connection under Ptygmatis Jonesit. 
156. Nerina (Ptygmatis) propuota, Witchell, 1887. Plate XV, figs. 10 a—e. 
1887. Nertnma propucta, Witchell. Vol. cit., p. 34, pl. i, fig. 18. 
Description : 
Spiral angle (regular) 3 : 3°. 
Height of whorl to width : feds 
Kstimated 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 
