NERITOPSIS. 339 
1851. PrtuoLus tHvis, Sow. Morris and Lycett, Great Ool. Moll., pt. i, p. 60, 
pl. ix, figs. 37, 37 a, 37 5. 
1852. — — — @Orbigny, Terr. Jur., ii, p. 240, pl. ceciv, figs. 1—4. 
1854. —_ — G. Sow. Morris, Cat., p. 268. 
PSyn. PareLLa MamMMitiaris, Miinst. Goldf., Petref. Germ., pl. clxvii, fig. 10. 
Description : 
Height. ; : : . 1:35 mm. 
Basal length ‘ : od man 
Shell elliptical, extremely depressed, apex subcentral; surface smooth, or only 
marked with indistinct furrows; the cushion is central; there are no indications 
of any crenulation on the inner lip. © 
Relations and Distribution—It is not possible fully to verify Sowerby’s 
diagnosis either for this or the preceding species. Morris and Lycett recognise 
the form in the Great Oolite of Minchinhampton. D’Orbigny’s figure may 
represent this species, though it is too orbicular. 
A single specimen from the “ Base bed,’ Lincoln. Quoted from the Inferior 
Oolite of the Cotteswolds by Morris and by Witchell. 
Family—NERITOPSIDA. 
* Shell neritiform or naticiform, imperforate, solid; aperture entire, semilunar 
or oval; lip arched; columella slightly excavated, internal septa not entirely 
absorbed. Operculum calcareous, thick, non-spiral.”’—FiscuEr. 
This family is limited to the genera Neritopsis and Naticopsis, whose opercula 
have in former days puzzled alike the Mesozoic and Palxozoic palzontologist. 
Genws—Neritopsis, Grateloup, 1852. 
Shell imperforate, subglobular, neritiform, solid, few-whorled ; spire short ; 
surface ornamented with spiral bands and axial ribs or striw. Aperture semicircular, 
entire, columellar side not denticulated, excavated towards the middle; lip simple, 
thick. Operculum seutiform, not spiral ; upper surface provided with a wide truncated 
appendia which fits into the columellar notch.—Modified after Fiscurr. 
It must be admitted that none of the specimens figured in illustration of this 
Monograph, though as good as any which can be procured on this side of the 
Channel, exhibit the columellar notch so characteristic of Neritopsis. Moreover 
