318 GASTEROPODA OF THE INFERIOR OOLITE. 
graph. Hence there is a sort of natural tendency to identify the British forms 
with Thorent’s species from the Inferior Oolite of the Aisne. As regards the 
form of tuberculation, Discohelix spinosus more nearly resembles it. The fossils 
now under consideration merely represent a modified form of Discohelix spinosus on 
a higher horizon, but they are flat atop and not biconcave: hence, according to 
the distinction adopted, they belong to Straparollus; and thus in structure, and 
probably in habit of growth, they most nearly resemble the original Huomphalus 
tuberculosus. From the fact of Morris having quoted “ Bridport”’ as the locality, 
I have very little doubt that he was referring to the form now under consideration. 
Description : 
Diameter. : : : . 15mm. 
' Height : , : : - mm. 
Shell depressed, discoidal; under surface largely excavated, upper surface 
nearly flat or slightly concave. The whorls are quadrangular, with flattened sides, 
which exhibit a very shght tendency towards contraction anteriorly. The 
marginal keels are grossly tuberculated, both on the upper and under side; on the 
flanks of the body-whorl these tuberculations almost extend across. Spiral 
ornamentation very faint; striz of growth conspicuous, perpendicular or curved. 
Aperture quadrangular, spiral and axial diameters nearly equal. 
Relations and Distribution.—The affinities of Str. tuberculosus-dexter have 
already been partly discussed. It differs from the French fossil in its dextral 
habit, and to some extent in the shape of the tuberculations. There are no 
sinistral forms in the Inferior Oolite of this country, but Straparollus sinister 
makes its appearance in our Middle Lias precisely as it does in France. Hence 
it seems to me that a dextral habit in our shell is an important element of 
difference. 
There are two specimens in my Collection from the Parkinsoni-zone of Burton 
Bradstock, besides one in the Jermyn Street Museum evidently in a similar matrix, 
and another from (?) Dundry. Small specimens from Hook Norton (C or upper 
part of B of Mr. Walford’s classification) approach the Burton Bradstock fossils, 
though with a leaning towards Solarium disculum, Morris and Lycett. There is 
also a specimen from the Lincolnshire Limestone of Stoke Lodge, which in some 
respects has more resemblance to Thorent’s figure than any previously examined. 
251. SrRAPAROLLUS PULCHRIOR, sp. nov. Plate XXV, fig. 9. 
Description : 
Diameter. ‘ : ae . 20 mm. 
Height ; : : : 2 6mm: 
