PULMONATA. 101 



P. testa lavi sub-striatdve, superne sub-pland, subtus concavd ; anfractibus sex vel 

 septem, rotundatis, vix involventibus, in/erne ad marginem umbilicalem sub-angulatis ; suturis 

 profundis : aperturd parum obliqud. 



A rather large shell, formed of six or seven nearly round volutions, separated by a 

 deep suture, and each slightly impinged upon by the preceding one ; the volutions 

 are flatly convex on the upper sides, convex beneath, and, like those of P. euomphalus, 

 present an angle running round the inner margins near the umbilicus, which, as the 

 shell approaches maturity, becomes almost obsolete. The upper face is nearly flat ; 

 while the under side presents a moderately deep and wide concavity. The aperture 

 is transversely oval, and but slightly oblique. The striae of growth are very conspi- 

 cuous ; and occasionally, although very rarely, the shells present fine concentric lines, 

 similar to those which characterise P. euomphalus ; in this species, however, the lines 

 are finer and more crowded, and seldom extend beyond the first three or four 

 volutions. 



Brard states that, in P. arrondi, the whorls are perfectly round, and do not impinge 

 upon the succeeding whorls ; and in these respects his shell does not agree with the 

 English specimens ; but the figures, apparently, are taken from a cast, and the dis- 

 agreement may probably be attributed to that circumstance. Brogniart's fig. 4, (var. 

 a, of that author,) agrees very well with our specimens, except that the aperture is 

 more oblique. In the figure given by M. Deshayes, the whorls are wider and more 

 flattened on the upper surface, and the upper margin of the aperture appears to be 

 more produced than in any English specimen I have seen ; the shell, too, is larger 

 than our shells, and, in fact, strongly resembles those specimens of P. euomphalus in 

 which the characteristic angle round the whorls has become obsolete. 



The general resemblance and the distinctions between the present species and the 

 recent P. corneus, have been pointed out by the French authors cited ; and, on com- 

 paring the two, it will be seen that in the latter species the whorls are fewer, rounder, 

 and enlarge more rapidly, and that in consequence, the shell is deeper and more 

 largely umbilicated than the fossil species. 



MM. Ferussac and Deshayes mention a variety (probably the var. b of Brogniart) 

 in which the shell is smaller, rather more compressed, and nearly equally concave 

 above and below ; I have not met with this variety among the English specimens. 



Size. — Diameter, 1 inch and 2-10ths. 



Localities. — English : Sconce ; Headon Hill ; Hordwell. French : Aurillac, La 

 Vissiere, Lavergnol, in the Cantal; Saint-Prix; Palaiseau, Milon near Versailles; Triel; 

 Fontainbleau ; La Villette. 



