340 EOCENE MOLLUSCA. 
5. Assim1nEA, Leach, 1816. 
“ Operculum horny ; paucispiral nucleus on the inner side of the mouth.” 
Type. Assiminea Grayana, Leach. 
6. Hyprosia, Hartmann, 1821. 
“Operculum horny and thin, marked with flexuous and rather strong lines of 
growth, and having a small lateral spire of three whorls.” 
Type. Turbo ulvee, Pennant. 
7. Nematura, Benson, 1836. 
“Operculum spiral, horny, of few volutions, somewhat concave externally, rather 
larger than the aperture.” 
Type. Nematura Delta, Benson. 
P 8. Vanvata, Willer, 1874. 
“ Operculum horny, circular, slightly compressed in the middle, forming a concentric 
spire of from 10 to 12 whorls, the outer edges of which are thickened and raised so as 
to project over and partly overlap the succeeding whorl.” 
Type. Nerita piscinalis, Miller. 
Genus 13th.—Puanorbis. Geoffroy, 1767. 
For generic character see ante, p. 97. 
No. 262. PranorBis Lavicatus ? Deshayes. Tab. XXXIV, fig. 1 a—é. 
PLANORBIS L&VIGATUS, Desh. Coq. foss. des Env. de Par.,t. xi, p. 85, pl. x, figs. 1, 2, 
1824. 
— = Id. An. sans Vert. du Bas de Par., tom. ii, p. 746, 1858. 
—_ — Prestwich. Geol. Journ., vol. x, p. 118, 1854. 
_ — Whitaker. Geol. Surv., vol. iv, p. 576, 1872. 
Spec. Char. “Pl. Testa discoided, levigatissimd, tenui, symmetricd, depressd, 
rotundatd, anfractibus quaternis, valdé apparentibus ; utroque latere umbilico equali.”— 
Desh. 
Diameter, =3;ths of an inch. 
Locality. Brit.: Dulwich (Boft.), Counter Hill (Whitaker), Peckham (Meyer). 
France: Bernon, near Epernay (Deshayes). 
Two or three specimens of this species have been found in our English beds, but all 
that I have seen are in the condition of casts; they, however, appear to correspond with 
