350 EOCENE MOLLUSCA. 
NERITA TRICARTINATA, Morris. Catal. Brit. Foss., 2nd edit., p. 264, 1854. 
= = J. Lowry. Chart Brit. Tert. Foss., pl. iii, 1866. 
Spec. Char. WN. Testé ovata, supra convexd, subtus convexiuscula ; anfractibus tribus, 
ultimo magno, spiraliter tricarinato ; spird retusd ; aperturd semicirculari ; ared columellart 
plana, margine minuté denticulato, labro acuto. 
Diameter, 35;ths of an inch. 
Localities. Bracklesham (£dwards). 
France: Retheuil, Cuise-la-Motte, Houdan (Deshayes). 
The figure I have given is from a specimen in Mr. Edwards’ cabinet. The shell has 
a fine denticulation on the sharp edge of the columella, but appears to be destitute of any 
prominent tooth on that edge, so far as I have been able to detect, in which respect it 
seems to agree with Deshayes’ figure. ‘Ihe imside of the outer lip, however, appears to 
be free from those denticulations which usually ornament those species which are grouped 
under the generic name JVerita. This species is especially distinguished by being 
ornamented with three prominent spiral ridges, between which the surface is covered with 
regular and somewhat fine striz. This species is said by M. Deshayes to be common in 
some localities of the Paris Basin, especially in the sands of Cuisse-la-Motte. He also 
observes that several varieties of it occur in the Calcaire grossier. I am not aware of its 
having occurred in England in any other bed than the Bracklesham. M. Deshayes thus 
describes the operculum of this species (‘ An. sans Vert. du Bas. de Par.,. t. iii, p. 17) :— 
“Tl est lisse en dessus, obliquement partagé par une étroite depression, qui part du 
sommet. Il est fort remarkable en ce qu'il porte deux apophyses ; lune sudapiciale, 
bifide, c'est celle qui existe invariablement dans toutes les espéces; Vautre mediane 
consiste en une proéminence aplatie et pointue, qui glisse en dessous du bord 
columellaire.” 
