230 GASTEROPODA OF THE INFERIOR OOLITE. 
Turritella opalina group. 
The following species or sub-species of Turritella, occurring in the Inferior 
Oolite of England, are placed in this category. Twurritella abbas, sp. u., T. opalina, 
Quenstedt, and var. canina, Hudleston, 7’. strangulata, sp. n. These forms may 
belong to the genus Mathilda. 
167. Turrivetta (Mathilda) appas, sp. nov. Plate XVII, figs. 2a, 26, 2¢— 
cf. Turritella septemeincta, Miinst., 
Goldf., Pl. 196, fig. 12. 
Description : 
Spiral angle : : : . 9—I11°. 
Height of whorl to width ; op es alge 
Approximate length , - 7 Oemm: 
Shell elongate, turrited, much indented by He sutural sulcus. Number of 
whorls from 16—20. Indications of a sinistral apex have been observed on one 
specimen. Between the subapical and anterior whorls there is but little difference 
except as to size; in shape the whorls are narrow and subtumid, the chief 
protuberance being postero-mesial, with a tendency to be pinched in at either 
extremity. The spirals are seven in number; usually there is a slight space 
between the first spiral and the suture, the second spiralis about equidistant, both 
are situated in a depressed’ area and are small. Between the second and third 
spirals there is a sharp rise of the whorl, and upon the most salient portion occurs 
the third spiral, which is the largest of all and constitutes the principal promi- 
nence; it might almost be described as a carina; the fourth and fifth spirals are 
nearly as large, the sixth spiral is sometimes small, the seventh spiral occupies 
the base of the whorl close to the suture. These ornaments are subject to a 
certain amount of variation in individual specimens ; both the spiral and the inter- 
spiral spaces are cross-hatched, but in this species the spirals are not deeply cut 
or granulated. Specimens such as fig. 2 ¢ exhibit some difference as to the size of 
the spirals; for instance, the sixth spiral is large and the whorls rather more 
tumid, showing, in fact, a passage towards the form recognised as 7’. opalina. 
The base is very flat and has from two to three spiral ridges; aperture ovate 
with a slight tendency to be subquadrate anteriorly. 
Relations and Distribution.—Turritella abbas clearly differs from T. opalina in 
the narrow and elongate character of the whorls. As regards 7. septem-cincta, 
