404 GASTEROPODA OF THE INFERIOR OOLITE. 



338. Plkukotomaria Obornensis, sp. nov. Plate XXXIV, fig. 9. 



Description : 



Height . . . . .44 mm. 



Basal diameter . . . . 36 mm. 



Spiral angle ..... 52°. 



Shell conical, elongate, with a slightly concave spire. Number of whorls 

 nine or ten, but slightly excavated and rather narrow, the body-whorl occupying 

 about one-fifth of the entire height. Bach whorl is terminated by a wide, 

 flattened, and richly sculptured basal rim or border, slightly undercut by the 

 succeeding whorl, the rest of the whorl being marked by subreticulate ornament, 

 in which the spiral element predominates. 



The sinus-band is anterior, but not markedly so, owing to the great width of 

 the basal rim ; it is rather narrow and fairly prominent, with one strong median 

 spiral and the usual cross-hatchings. In the body-whorl all the ornaments, 

 even those of the basal rim, become smooth, and the sinus-band is rounded, 

 narrow, and prominent. Base nearly flat or with a very slight concavity, spirally 

 striated, with some radial decussation. Aperture oblique and depressed. Other 

 indications wanting. 



Relations and Distribution. — The excessive flatness and great width of the 

 basal rim serve to separate this elegant conical shell from members of the 

 elongata-growp generally. In the richness of its sculpturing it approaches 

 PI. Agatha, but presents important differences. Very rare in the Sauzei-bed 

 (Marl with green grains) at Oborne. 



339. Pleurotomaria circumsulcata, d'Orbigny, 1854 (= PI. mutabilis, Deslong- 



champs, pars). Plate XXXIII, figs. 3 

 and 11 ; and Plate XXXIV, fig. 3. 



1854. Pleurotomaria circumsulcata, d'Orbigny. Terr. Jur., vol. ii, p. 470, 



pi. ccclxxxi, figs. 6 — 10. 

 ttyn. mutabilis, Deslongchamps, var. circumsulcata. Vol. 



cit., p. 112, pi. xi, tig. 2. 



The spiral angle is about 70°, and very distinctly concave. Unless the base is 

 well exposed and in good preservation, the submarginal furrow which constitutes one 

 of its peculiar features cannot be observed. The original figure by Deslongchamps 



