232 GASTEROPODA OF THE INFERIOR OOLITE. 
figure, wider spiral angle, and by the shorter and more tumid whorls. The details 
of ornamentation also differ considerably. 
But just as there are specimens, such as fig. 2c, which seem to connect 
T. abbas with T. opalina, so also there are specimens which serve to bridge over 
the gap between 1’. opalina and T. quadrivittata. On the other hand fig. 3b repre- 
sents a richly ornamented and unusually well-preserved specimen of 7’. opalina, 
where the sulcus between the two principal carinz is occupied by a secondary 
spiral, thus adding to the number. 
A single specimen of 7’. opalina has been found in the opalinus-bed of Burton 
Bradstock. A few in a better state of preservation have been obtained from the 
concavus-bed, Bradford Abbas. It may also occur in the Dogger at Blue Wyke 
and in the Millepore-bed. 
169. Turriretta (Mathilda) opauina, var. cantina, Hudleston, 1884. Plate XVII, 
fig. 4. 
1884. TuRRITELLA OPALINA, Quenstedt, var. cantNA, Hudl. Geol. Mag., dec. 3, 
vol. i, p. 200, pl. vii, fig. 9. 
Description : 
Spiral angle ; ; ; . 20°—23°. 
Height of whorl to width ; j 2 hates 
Approximate length . : 5 . 40 mm. 
This variety possesses the conical shape of T. opalina, but under a wider spiral 
angle, and the relative width of the whorls is greater. The whorls are very short 
and globose, and separated by a well-marked sutural sulcus. The apex is unknown; 
the subapical whorls are globose and have about seven spirals; the more mature 
whorls have about eight. Of these, three nearly equal strap-like bands are 
distinguished, occupying the area a little below the centre, the uppermost of the 
three being slightly the strongest and representing the most salient portion of the 
whorl. Owing to the crowding of the spirals (and partly also to the peculiarity of 
the matrix) the cross-hatching is not conspicuous. Aperture similar to that of 
T. opalina, but slightly more orbicular. 
Relations and Distribution.—The relations of this variety to other members of 
the opalina-group have been already indicated. A very few specimens have been 
found in the Dogger at Blue Wyke. Specimens approaching this variety, such as 
fig. 5 b, occur in the concavus-bed, Bradford Abbas. 
