120 GASTEROPODA OF THE INFERIOR OOLITE. 



The specimen figured lias 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 Alarice. Available specimens are 

 generally wanting in some feature of importance. In the present case, if we were 

 sure that Al. unicornis possessed a second spine, opposite the wing, this feature 

 would serve still more closely to connect it with Al. unicarinata, 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. unicarinata. 



Very rare in the Oolite-Marl of the Cotteswolds. 



40. Alaria : Cf. unicornis, Lycett. Plate V, figs. 7 a, 7 b. 



Description : 



Length . . . . .26 mm. 



Width of body- whorl to height of shell . . 42:100. 



Spiral angle ..... 28°. 



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 costas 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 costse, though marked by longitudinal striae. 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, i. 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 

 Murchisona-zone. If a varietal name is required I would suggest that of Brad- 



FORDIENSIS. 



