NERIN AA. 219 
The section of the type is unknown; a specimen from the Pea-grit of 
Longfords, showing the posterior half (fig. 9c), gives indications of a structure on 
the bacillus or Oppelensis plan. A section of the anterior half (fig. 9b) gives faint 
indications of a similar character. 
Relations and Distribution.—Owing to the fact that the two portions of this 
very dimorphous form are rarely found in one piece, a degree of uncertainty hangs 
about the species. Posteriorly its relations with Ptyg. bacillus are intimate, but 
the anterior portion is quite different. From Ptyg. Oppelensis it is separated by 
the height of the whorls and by its more elongate habit. 
Rare in the Freestone, Nailsworth, and in the Pea-grit at Longfords. 
A specimen from the Lincolnshire Limestone of Wakerly (figs. 8a and 8d), 
which I temporarily designate as Ptygmatis “ baccilloides,” reminds us of the pos- 
terior portion of Ptyg. Jonesii, though the whorls are a little shorter. 
The section of the Wakerly fossil seems to be on the bacillus-Oppelensis plan, 
but it possesses considerable peculiarities of its own, which at present require the 
confirmation of other specimens. 
155. Nerinma (Ptygmatis) Orprtensis, Lycett, 1857. Plate XV, figs. 11 a—e. 
1857. Neninza Oppenensis, Lycett. Cotteswold Hills, p. 123, pl. ii, figs. 6, 
6 a. 
1887. _— — — Witchell, vol. cit., p. 30, pl. i, fig. 3, 3 a. 
Bibliography, §c.—Originally described from a fragment found in the Oolite 
Marl of Selsley Hill. Witchell considered the section shown by Lycett to have 
been much worn. Accordingly he substituted another, which is again figured 
(fig. lle). This figure, he says, occurs with slight variations in four Inferior 
Oolite species. This number may be increased. 
Description : 
Spiral angle (mean) . : : 0 2G 
Height of whorl to width : ional iede 
Approximate length . ; ; . 80mm. 
Shell conical to cylindrical, dimorphous. The spire has a bluntish apex, and 
the apical angle is nearly double the mean spiral angle, so that the general angle 
is very obtuse. Whorls twenty-five and upwards, short, with indications of spiral 
ornament in the earlier stages. The apical whorls are deeply excavated, the spiral 
belt being thick and prominent. These features gradually soften down until we 
reach the stage described by Lycett, where the whorls are “ slightly tumid at the 
junctions,” and the excavation is but slight. In specimens from the marly Lime- 
