414 GASTEROPODA OF THE INFERIOR OOLITE. 



Whorls (about seven) flat to slightly convex, sutures rather close and not canalicu- 

 late. Spiral ornamentation is faintly inscribed thoughout the apical whorls, but 

 in the later whorls it is only seen in the anterior areas ; traces of radial ornamen- 

 tation slight. 



The sinus-band is narrow and inconspicuous ; it is nearly mesial, or only slightly 

 anterior. The body-whorl occupies about half the height of the shell, aDd is 

 bluntly angular towards the base, which is rather flat with faint spiral striae. 

 Indications respecting the umbilicus not very clear; aperture nearly square. 



Relations and Distribution. — The conoidal figure, almost flat whorls, and non- 

 canaliculate sutures serve to distinguish this form from PI. monticulus, which it 

 otherwise greatly resembles. Rare on a low horizon at Haselbury and Coker. 



352. Pleorotomaeia (Leptomaria) sulcata- Humphriesiana, sp. nov. Plate XXXV, 



fig. 11. 



N.B. — It is not without much hesitation that I venture in this case to make a 

 new species. The form now under consideration occupies a position midway 

 between — 



Pleurotomabia Agathis, D e si on g champs. Vol. cit., p. 139, pi. xiii, fig. 8, 



and 

 — sulcata, Deshayes alter Soiverby. DesloDgeliamps, vol. cit., p. 135, 



pi. xiii, fig. 4 = PI. unisulcata, d'Orbigny. 



Description, : 



Height . . . . .24 mm. 



Basal diameter . . . .31 mm. 



Spiral angle ..... 80°. 

 Shell conical, largely and deeply umbilicate. Spire almost regular, with a sub- 

 acute apex. Whorls (seven) slightly convex, and with rather faint spiral orna- 

 ment, often decussated posteriorly by sinuous growth-lines. There are two varieties, 

 one where the suture is slightly canaliculate and the whorls subangular, another 

 where the whorls are rather undercut. In some specimens the radial ornament 

 on the posterior area of the whorls is strong. 



The sinus-band is very narrow, and situate slightly below the middle of the 

 whorls, and in the subangular variety occupies the prominence. The body-whorl 

 is bluntly angular at the periphery; base scarcely convex, smooth, or only marked 

 with faint radial stria). Umbilicus steep and " staircase-like." Aperture nearly 

 square, inner lip straight and rather thickened, being slightly removed on the 

 columella. 



