400 GASTEROPODA OF THE INFERIOR OOLITE. 
aperture subquadrate and moderately depressed with a slight columellar notch, 
not always preserved. 
Var. angusta (Fig. 4). 
This represents a form which may be noted in the Lower Division of the 
Inferior Oolite, where the spiral angle does not exceed 40°, and in some cases, 
as in the Opalinus-zone at Drympton, is even less. The specimen figured is 
from Bradford Abbas (? Murchisonx-zone). Another specimen (Fig. 5), from the 
Concavus-bed of Bradford Abbas, presents a wider spiral angle besides some 
difference of ornamentation. 
Var. near to Pl. conoidea, Deshayes (Fig. 6). 
1831. Prevroromarta conorpEa, Deshayes. Coq. caract., p. 181, pl. iv, fig. 4. 
This is a variety with extremely rich sculpture; the spiral angle in some 
cases is slightly concave, whilst the sinus-band is very anterior and not at all 
prominent.' These forms occur at Mapperton, Louse Hill, and other places 
believed to be in the Humphriesianus-zone. 
Pleurotomaria elongata, Sowerby. Type form (Fig. 7). 
Cf. 1854. Prevroromarta Prcraviensts, d’Orbigny. Terr. Jur., vol. ii, p. 510, 
pl. ceexcix, figs. 1—5. 
— _ MUTABILIS, var. AMBIGUA, Deslongchamps. Vol. cit., 
p. 118, pl. xi, fig. 1. 
This is a robust form with spiral angle of about 50°. It more nearly 
approaches Sowerby’s type (one of the three species-types preserved in the 
British Museum’) than any of the others. In this variety the sculpture is 
principally seen in the more apical whorls; the basal rim of the anterior whorls 
being thick, round, and nearly smooth, whilst the spiral striz in the whorls 
themselves are less deeply incised. The sinus-band in the lower whorls is smooth 
and very anterior; striz in the base indistinct. Aperture subquadrate and 
moderately depressed ; traces of the columellar notch very slight. 
Characteristic specimens occur abundantly at Dundry and in the Sauzei-bed 
(base of the Hwmphriesianus-zone) at Combe and Oborne. Some persons might 
be disposed to restrict the specific name, elongata, to this form. 
1 Mr. Wilson considers that P/. eonoidea should be regarded as a distinct species, as he attaches 
great importance to the want of prominence in the sinus-band. 
2 Vide antea, p. 396. 
