224 GASTEROPODA OF THE INFERIOR OOLITE. 
tinguish Ptygmatis Cotteswoldix from any species hitherto described in this 
Monograph, but it has affinities 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 Geddington, 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, the upper beds of the Lincolnshire Limestone show but doubtful traces, 
and in the Great-Ponton cutting there are none. 
161. Neriwma (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. Cotteswoldix. 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 only differs from Ptyg. Cotteswoldix 
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. Nerinaa (Ptygmatis) Sanvonis,’ sp. nov. Plate XVI, figs. 8 a—c. 
Description : 
Spiral angle (regular) ; pe rieks 
Height of whorl to width . : padle sl SAr 
Length ; ; . 70—100 mm. 
Shell cylindro-conical, sightly dimorphous. Whorls twenty to twenty-two in 
well-grown specimens. ‘The subapical whorls are flat, and this portion of the 
1 N. Santonensis, D’Orb. (1. J., vol. ii, p. 156), is a “ Portlandian ” species of Merinea. 
