434 GASTEROPODA OF THE INFERIOR OOLITE. 
Bibliography, §ce.—It should not be forgotten that the types of Pl. actinomphala 
occur in the “ Maliére ” of Normandy, a bed underlying the ‘‘ Oolithe ferrugineuse.”’ 
Deslongchamps speaks of it as being common in the condition of casts. It so 
happens that in the Concavus-bed at Bradford Abbas, which should be somewhat 
about the horizon of the “ Maliére,”’ i.e. in the Lower Division of the Inferior 
Oolite, a group of Plewrotomaria occurs, exhibiting great variety both as to size 
and form, but which, without using varietal names, it may be convenient to focus 
under Pl. actinomphala. 
Similarly, it seems probable that considerable variety exists in the specimens 
from France, if we are to regard the figures of Deslongchamps and d’Orbigny as 
representing the same species. 
Description.—Amidst a multiplicity of fossils of all ages and sizes, and with 
much variety of character, there are two groups of varieties which attract our 
attention. 
Acute Variety (Pl. XXXVII, fig. 7, and Pl. XXXVIII, fig. 5).—The form is 
conical, and the shell may have a smooth periphery as in the first figure, or a 
rugose periphery as in the second. Generally speaking, this form is rugose in 
ornament, and it seems, on the whole, more nearly to represent the Pl. actinomphala 
of the French authors. It is also intimately related to Pl. oxytera, described above, 
though the whorls are always more tabulate. 
I have specimens of this variety, chiefly from the Concavus-bed at Bradford 
Abbas and Halfway House, also from Dundry, and even from the neighbourhood 
of Sherborne. 
Obtuse Variety (actinomphala-abbas) : 
Height (moderate size) . é . 42 mm. 
Basal diameter : : : . 65 mm. 
Spiral angle . : . 110°—115°. 
Shell turbinate, depressed, largely Geilicate! Spite regular ; apex subacute. 
Whorls (seven) subangular and inclined to be tabulate, increasing by steps ; in the 
spire-whorls the suture is canaliculate. On the crest of each whorl is a corona of 
tubercles, which are regular, and there is a certain amount of spiral ornamentation, 
which is rather worn off in the older specimens ; there is no trace of a second carina 
or belt at the base of the whorls. 
The sinus-band is median, wide, and flat, showing some spiral lines in the 
younger and better preserved specimens, but usually smooth and strap-like in the 
later ones. The body-whorl is relatively very large, convex, and biangular, the 
anterior angle being nodular to smooth according to age and condition. The base 
is convex and without much trace of spiral ornament, except in very young shells ; 
umbilicus wide, steep, and like a “ staircase” in the earlier stage, with large ribs 
radiating therefrom, though scarcely reaching the margin. In the old shells these 
