PLEUROTOMARIA. 405 
represents an acutely conical shell with a concave spiral angle and tuberculated 
carinz. Hence the species seems to occupy a position between Pl. abbreviata and 
Pl. Bessina. 
I have a small specimen (Pl. XXXIII, fig. 11), from the Parkinsoni-zone of 
Burton Bradstock, which plainly shows the submarginal furrow in the base. In 
this specimen the sinus-band is narrow and prominent; it corresponds precisely 
both in size and structural details with specimens from the Parkinsoni-zone of 
Bayeux, which are generally referred to Pl. circwmsulcata. he other figured 
specimens, which are referred with some doubt to Pl. circumsulcata, correspond as 
regards spiral angle and general ornamentation, but they do not show a well- 
developed marginal furrow in the base, 
340. PLEUROTOMARIA SUBGLABRA, sp. nov. Plate XXXIV, figs. 1 and 2. 
Description : 
Height 5 : 5 . 48 mm. 
Basal diameter : ; , . 55 mm, 
Spiral angle (mean) . : : » 682: 
Shell acutely conical, scarcely umbilicate. Spire markedly concave. Full 
number of whorls about eleven; these are flat or only very slightly excavated, 
with a very close suture. The earlier whorls are terminated by a shght basal rim 
or carina, but in the later whorls this feature is almost effaced, although the 
spirals at the base have somewhat larger granulations where we should expect to 
find the basal carina; the rest of the whorl is ornamented with fine spiral striz, 
more or less decussated, the strize in some cases being so delicate that the shell 
becomes almost smooth. 
The sinus-band is very anterior ; it is narrow, and more prominent in the coarsely 
ornamented than in the finely ornamented specimens, but it is not, on the whole, a 
conspicuous feature. The body-whorl projects somewhat beyond the angle of 
the spire, the periphery being slightly rounded off; base flat to subeonvex, with 
spiral striz corresponding to those on the flanks of the shell. There is a small 
umbilical hollow, but no true umbilicus. Aperture subrhomboidal and oblique, 
with but a faint trace of the columellar notch. 
Relations and Distributions—The concave spire serves to remove Pl. ctrcwm- 
suleata, Pl. subglabra, and Pl. Bessina from Pl. abbreviata. Yet we may expect to 
find links in the chain. Thus Pl. subglabra, which is probably only a glabrous 
variety of Pl. circwmsulcata, constitutes an intermediate stage between Pl. abbreviata 
