528 BRITISH PAL/EOZOIC FOSSILS. [GasTERopopA. 
longitudinal wrinkles, very slightly oblique to the band, forming an obscure, irregular, quadrate pitting, 
occasionally visible on the cast ; these transverse plicze closer and more oblique on the base ; band about the width 
of the ordinary spaces between the spiral lines, flat, very inconspicuous, and bounded by very delicate, impressed 
lines, destitute of the obtuse cancellating plicze of the rest of the surface, situated two inter-spiral spaces above the 
lower suture of each whorl. Width ten lines, proportional height of last whorl 3, height of penultimate 
whorl *., width of mouth 4. 
Var. 8. Very elongate, conic, apical angle about =; whorls moderately convex; base of basal whorl 
gradually prolonged, not flattened nor separated by any angulation from the sides; mouth a little longer 
than wide. Length of last whorl eleven lines, proportional width <3, proportional height of penultimate 
40 
whorl 3. 
It will be seen that this species has two extreme varieties somewhat resembling those of the P. Yvanni ; 
the variety a so exactly resembles a Trochus, that it requires the most careful examination to detect the 
extremely obscure though definite band, to convince the observer that it is a Plewrotomaria ; the var. 8 with the 
basal whorl elongate, and rounded in front or at base, like the corresponding variety of P. Yvanni, is so like a 
Macrochilus that it is only by carefully tracing the intermediate forms, and detecting the very obscure band, 
noting the same number of spiral ridges on the whorls, &c., that I have become satisfied of their identity. 
Both varieties have usually only four whorls preserved ; the posterior end of the animal at that length depositing 
convex, imperforate diaphragms, and becoming naturally decollated. 
Position and Locality.—Both varieties rare in the impure lower limestone of Lowick, Northumberland ; the 
yar. 8 rare in the similar limestone of Kendal, Westmoreland. 
Explanation of Figures.—P|. 3. H. fig. 13, natural size, conical variety, from the carboniferous limestone 
of Lowick; fig. 14, ditto, elongate variety, with rounded whorls. 
PLEUROTOMARIA EROSA (M°Coy). PI. 3.1. figs. 38 and 39. 
Ref.—M°Coy, Ann. Nat. Hist. 2nd Series, Vol. XII. 
Desc.—Orbicular, depressed, very obtusely conical; apical angle 105°; spire of four and a half rapidly 
enlarging whorls; flattened, or very slightly convex ; sutures, fine, simple, impressed lines ; body-whorl flattened, 
or slightly convex in the upper two-thirds ; periphery very obtusely rounded close to the broad, flattened, gently 
convex base; umbilicus entirely closed, with a large, very thick, semicircular, shelly pad; band narrow, obscure, 
bounded by two fine impressed lines; surface glossy, eroded with deep, obtuse, excavated markings, without 
regularity in size, shape, or direction; lines of growth arching backwards to the band, scarcely visible. 
Diameter five lines, proportional height 4, height of mouth =, space between last and penultimate sutures 
width of umbilical pad +. 
The band of this species is often almost invisible on the periphery of the body-whorl, and lines of growth 
can only be traced here and there with a lens. The substance of the shell is very thick, and with the glossy 
surface, general form, and large umbilical pad, recalls Rotella (= Pithonellus) very strongly. The peculiar 
“worm-eaten” appearance of the irregular pitting of the surface is equally marked in the two specimens 
before me. 
Position and Locality.—Rare in the carboniferous limestone of Lowick, Northumberland. 
Explanation of Figures—P\. 3. 1. fig. 38, magnified half a diameter, under side, from carboniferous 
limestone of Lowick; fig. 39, profile, natural size; fig. 39 a, ditto, seen from above; 39 6, ditto, magnified 
half a diameter. 
20 
100? 
PLEUROTOMARIA GRIFFITHI (J/‘°Coy). 
Ref.—M°Coy, Syn. Carb. Foss. Irel. t. 6. f. 1. 
Dese.—Acutely conical, apical angle 85°, spire of five or six whorls, each very acutely angulated by the 
sloping of the upper and under surfaces to an extremely prominent, flat keel; truncated or quadrate at its 
