224 GASTEROPODA OF THE INFERIOR OOLITE. 



tinguisli Ptygmatis Cottesivoldise from any species hitherto described in this 

 Monograph, but it has aflSnities with some of the species that follow. The group 

 of which it is the type is characterized by very short whorls, which are flat and 

 unornamented in the anterior stage, and by a very restricted and whimsical 

 section. Specimens from the Pea-grit and from the Lincolnshire Limestone are, 

 as a rule, narrower than those from the Oolite-Marl horizon of the Cotteswolds. 



This species and its varieties are widely distributed, both vertically and hori- 

 zontally, but especially on the Oolite Marl horizon of the Cotteswolds. In the 

 Lincolnshire Limestone it occurs in the lower bed of Little- Ponton cutting, at 

 Wakerly, Belmisthorpe, and Geddiugton, and at the slate-pits of Kirby and Dene 

 Lodge, and probably at many other places. Of late a more cylindrical variety, 

 with some difference of internal structure, has been found in considerable numbers 

 in the lower beds of the Lincolnshire Limestone at Hungerton Hall. On the other 

 hand, tlie upper beds of the Lincolnshire Limestone sliow but doubtful traces, 

 and in the Great-Ponton cutting there are none. 



161. NBEiNiEA {Ptygmatis), species or variety. Plate XVI, fig. 6. 



The spiral angle is about 14°, the relative height of the whorls the same as in 

 Ptyg. Cotteswoldise. The whorls are slightly excavated, and the sutural prominence 

 is the most conspicuous at the base of each whorl, which causes it to overhang 

 the surrounding one. The internal structure on\y differs from Ptyg. Cotteswoldise 

 in the presence of an incipient additional fold on the upper part of the columella. 



This form diverges from Lycett's species more widely than the var. conica, 

 and to a certain extent in an opposite direction. But it may have been a diseased 

 or abnormal individual. A single specimen from the marly Limestone, Swift's 

 Hill. 



162. NERiNiEA (Ptygmatis) Santonis,^ sp. nov. Plate XVI, figs. 8 a — c. 



Description : 



Spiral angle (regular) . . .8°. 



Height of whorl to width . . . 1 : 1'4. 



Length .... 70—100 mm. 



Shell cylindro-conical, slightly dimorphous. Whorls twenty to twenty-two in 

 well-grown specimens. The subapical whorls are flat, and this portion of the 



' JS\ Santonensis, D'Orb. (T. J., vol. ii, p. 15GJ, is a " Portlaudian " species of Nerinaea. 



