444 GASTEROPODA OF THE INFERIOR OOLITE. 
possibly also of the higher parts of that zone. I have one specimen from 
Shotwell, which in all respects corresponds with d’Orbigny’s figure. The 
specimen figured in the accompanying plate (Pl. XL, fig. 3) is between this 
extremely smooth form and the ordinary Pl. plicopunctata. 
385. PLEUROTOMARIA TRAPEZA, sp. nov. Plate XL, figs. 5a, 5b. 
Description : 
Height : : ; : . 3d mm. 
Basal diameter ; : : . 44 mm. 
Spiral angle . ‘ eon: 
Shell trochiform, subtabulate, dightly see icaied. Spire regular, with 
sharp apex. Whorls (seven) angular, and increasing by steps; the posterior area 
has a moderate slope, whilst the anterior area (below the sinus-band) is almost 
perpendicular, and constitutes a broad costated girdle round each whorl; sutures 
close. The spiral system is overpowered by strong radial coste, which are 
oblique above the sinus-band and axial below. 
The sinus-band is narrow and prominent, being situated mesially at the angle 
of the whorl; owing to its prominence the ornaments seem worn. The body- 
whorl is large and bluntly angular at the periphery, so as to be slightly 
biangular. Base very convex, with spiral ornamentation stronger than the 
radial; umbilicus small. Aperture subquadrate 
Relations and Distribution.—Intermediate forms between this and the larger 
varieties of Pl. plicopunctata may be noted, and yet there is a tolerably sudden 
jump at last; whilst in the narrowing of the spiral angle there is a sort of return 
to Pl. granulata of the lower horizon. Still I do not doubt that this is a kind of 
offshoot from the common “granulate” Plewrotomaria of the Parkinsoni-zone 
(i.e. Pl. plicopunctata). Moreover it is of importance with reference to the 
occurrence of a tabulate form connected with the Granulate on higher horizons, 
such as Pl. granulata, Lycett, of the Scarborough Cornbrash, and even Pl. 
Miinsteri, Rim. (Pl. filigrana, Deslongch.), of the Lower Corallian. See page 440 
with reference to Morris’ identification of Pl. granulata on different horizons. 
Pl. trapeza is found at Burton Bradstock, and may be expected to occur at 
Broadwinsor, and other localities of the Parkinsoni-zone. 
