TURRITELLA. 
231 
Miinster, that species was founded on a fragment, some 12 mm. in letigth, said to 
come from the Lias. The enlargement by Goldfuss shows a whorl not dissimilar to 
that of T. abhas ; but, as we are left in doubt on many points, it is safer to make a 
new species in this case, and I am the more inclined to do so because T. abbas is 
decidedly the characteristic and most abundant Turritella in the Inferior Oolite of 
Dorsetshire. 
T. abbas occurs chiefly in the concavus-hed at Bradford Abbas, where fragments 
are not uncommon ; it also occurs in the corresponding zone near Beaminster, 
and has been noted rarely in the Pea-grit of Crickley. 
168. Tureitella {Mathilda) opalina, Quenstedt, 1858. PI. XVII, fig. 3 a. 
1858. Txteeitella opalina, Quenstedt. Der Jura, p. 326, pi. xliv, fig. 13. 
Bibliography , 8fc. — This is most probably the Turritella elcmgata of Zieten 
(= Gerithium elongatum, d’Orb, Prod. 1, p. 250). The specific name elongata had 
been already appropriated by Sowerby for a Turritella of Tertiary age, cf. 
Hudleston, ‘ Geol. Mag.,’ dec. 3, vol. i (1884), p. 200. Quenstedt’s name may be 
accepted as a generalised term for elongate Turritellse of Jurassic age possessed of 
about six or seven spirals, but the following description relates to a specialised 
form which, it is believed, more distinctly resembles Quenstedt’s species. 
Description : 
Spiral angle .... 14° — 15°. 
Height of whorl to width . . . 1 : 1*75. 
Approximate length . . . .45 mm. 
Shell conical- elongate, spiral angle very regular, sutural sulcus wide. Whorls 
about fifteen, short and tumid, the chief prominence nearly mesial. Sinistral 
apex probable. Usually there are six spirals, the fourth and fifth being the most 
prominent ; between these two is a sulcus of considerable depth, the impression 
of which is left on the internal mould. The cross-hatching or axial ornamentation, 
as in the opalina-growp generally, is distinct, equally spaced, and but slightly 
oblique; the spirals are slightly granulated. 
Base very flat and slightly excavated ; aperture subcircular with a tendency to 
be subquadrate anteriorly, columellar lip short and straight. 
Relations and Distribution. — Quenstedt does not give a detailed description of 
T. opalina, but the fossils now under description correspond well in proportions, 
and to a certain extent in ornamentation with that author’s figure ; our examples 
are rather shorter. It is clearly distinguished from T. abbas by its more conical 
