PLEUROTOMARIA. 397 
figure (also from a Dundry specimen) is characteristic, though the aperture is not 
seen. The species does not appear to have been recognised by Deslongchamps in 
the Normandy beds. On the other hand, Tawney regarded it as one of the 
commonest species at Dundry. He suggested that Pl. Allionta, d’Orbigny, might be 
a synonym. 
Description : 
Height 5 : ; ‘ . 40 mm. 
Basal diameter : F ‘ . od mm. 
Spiral angle . ; , ; . 48°. 
Shell acutely conical, not umbilicate. Spire perfectly regular. Whorls 
(ten to twelve) flat, with a close suture, and spiral lines of unequal strength; these 
are more or less granulated towards the posterior and anterior margins of each 
whorl; the almost invisible suture lies between the raised limes which carry the 
strongest granulations. 
The sinus-band forms a salient belt on the sides of the whorls, and is situated 
some distance below the centre ; it is full, round, and rather narrow, having in 
the apical whorls a central spiral line crossed by growth-lines, but in the later whorls 
the growth-lines alone are seen, and even these are often effaced. The body-whorl 
is angular at the periphery ; the base has a flat marginal area, but is excavated 
towards the centre; it is spirally striated with slight radial decussation. Aperture 
subrhomboidal and extremely depressed. 
In the smaller shells the columellar notch is very characteristic (Fig. 2), and 
even in the larger shells a modification of this feature may be detected. In very 
large forms (? P/. Allionta) the notch is effete. 
Relations and Distribution.—Pl. punctata is a well-defined species, somewhat 
remotely related to the elongata-group. Excellent specimens have been obtained 
from Dundry. Good specimens are also obtained from the Murchisonx-zone of 
Coker, and inferior ones from the same horizon at Bradford Abbas. The Concavus- 
bed at Bradford Abbas furnishes us with a number of beautiful specimens. The 
above are all in the Lower Division. 
In the Humphriesianus-zone of North Dorset typical specimens may 
occasionally be met with. There is a large specimen in my collection, said to 
come from the Parkinsoni-zone, which may possibly represent Pl. Allionta, d’Orb. 
In this case there is no trace of the columellar notch. 
