226 GASTEROPODA OF THE INFERIOR OOLITE. 
its section partaking of the whimsical character of that abundant species, though, 
hke Ptyg. Santonis, it possesses only three folds on the columellar side. It is 
easily distinguished from all other species of Nerina previously described in this 
Monograph by the excessive shortness of the whorls. The width of a whorl is 
equal to its height plus the height of the preceding one, plus half the height of 
the next preceding one. 
Found in considerable numbers in the Clypeus-grit of Barrington, in the 
Cotteswolds, and noted also on the same horizon at Twerton Hill, near Bath. 
A fragment from the Lincolnshire Limestone of Weldon (fig. 10) presents 
similar proportions, and may at least represent a variety. 
164. Nerinua (Ptygmatis), species or variety. Plate XVI, fig. 11. 
Description : 
Spiral angle : ; : » Willie 
Height of whorl to width : 3 bon) dlssel Ze 
Length about : 5 : . 45 mm. 
This form differs from the preceding, chiefly in the greater relative length of 
the whorls, and consequent difference in the shape of the aperture. The section 
is pretty much on the same plan; but, as the folds were somewhat smaller, there 
was more interior space, the anterior fold on the columella being markedly less 
than in Ptyg. brevivoluta. 
A single specimen from the Lincolnshire Limestone of Weldon, to which I give 
the temporary name of ‘ sub-brevivoluta.” 
N.B.—In spiral angle and internal structure Ptyg. brevivoluta and the Weldon 
form rather remind us of the figure of N. subtruntrutana, D’Orb. (T. J. 2, p. 94, 
pl. ccliv, figs. 1 and 2), a species described by D’Archiac from the Bathonian of 
Eparey. But that species has a thoroughly conical figure and no sutural pro- 
minences. Moreover, the spiral ornamentation is very marked. 
