120 GASTEROPODA OF THE INFERIOR OOLITE. 
The specimen figured has a length of 26 mm. (exclusive of the fragment of the 
canal-sheath), and a spiral angle of about 30°. 
Relations and Distribution.—It is only piecemeal, as it were, that we can hope 
to work out the true relations of the Jurassic Alavrie. Available specimens are 
generally wanting in some feature of importance. In the present case, if we were 
sure that Al. wnicornis possessed a second spine, opposite the wing, this feature 
would serve still more closely to connect it with Al. wnicarinata, notwithstanding 
certain differences in the spire which are increased by difference of matrix. 
Again, we are not certain of the true character of the digitation of Al. wnicarinata. 
Very rare in the Oolite-Marl of the Cotteswolds. 
40. Auarta: Cf. unicornis, Lycett. Plate V, figs. 7 a, 7 b. 
Description : 
Length ‘ ; : : . 26mm. 
Width of body-whorl to height of shell —. . 42; 100. 
Spiral angle . ; ; ease 
Shell turrited, fusiform, elongate. Number of whorls about ten, excluding 
the apicals ; the whorls of the spire are very angular, and the keel placed rather 
far back, so as to make the anterior area twice as long as the posterior area. This 
peculiarity is less strong on the penultimate than on the other whorls of the spire. 
The coste are regular, very straight, and rather strongly marked, though becoming 
less well-developed in the anterior whorls. The spirals are fine and crowded 
posteally, much coarser, about four in number, below the keel. The body-whorl 
is entirely without coste, though marked by longitudinal striz. It is practically 
unicarinate, since the lower keel becomes effete before reaching the margin. The 
keel is very salient and carries two large spines :—a, the anterior spine, a quarter 
of a turn above the wing; p, the posterior spine, a quarter of a turn higher up, ¢. e. 
opposite the wing. 
The aperture is rudely triangular, the wing consists of one digitation, which 
is stout at the base, but has not been observed further. Canal staight, as far as 
observed. 
These shells occur rarely towards the junction of the Sowerbyi-bed and the 
paving-stone bed at Bradford Abbas, and may be regarded as belonging to the 
Murchisone-zone. If a varietal name is required I would suggest that of Brap- 
FORDIENSIS. 
