114 EOCENE MOLLUSCA. 
and ventral margins curved; lunule elongate, distinct, and rather depressed ; anal region 
heartshaped ; teeth small near the beak; margins smooth. 
Length, } an inch ; height, 3ths of an inch. 
Localities. Wighcliff, Barton, Brockenhurst, Hordwell (Zdwards). 
Although a thin and delicate shell, it has been obtained by Mr. Edwards in great 
abundance. The exterior is smooth and glossy, with a few concentric ridges or obtuse 
lines of growth. The interior has a strong nacreous lustre, with an enamelled exterior. 
The hinge-line is narrow ; it has about a dozen denticles on the pedal side, with scarcely 
half that number on the other, and the support for cartilage is simple, somewhat elongated, 
projecting inwardly at an angle of 45° to the dorsal margin. There is a deep depression 
(lunule?) on the pedal region, producing a sharp elevation to the dorsal margin, with a 
faint depression on the siphonal or anal region, but not very well defined. The extremity 
of the siphoni-lateral margin is rather short and generally more or less pointed or subro- 
strated ; this gives a considerable convexity to the ventral margin in the normal form. ‘The 
shell is thin, and the oral muscle scarcely visible, but the anal one is large and well 
impressed. 
There are, I think, three varieties of this species; at least, there are three different 
forms, which I have referred to the above name, presenting as they do considerable 
difference in outline, but not, I think, sufficient to entitle them to different Suseite 
positions. Tab. XX, fig. 1, a, 4, ¢. 
11. Nucuna minor, Deshayes. Tab. XVIII, fig. 10. 
Nucuia minor. Desh. An. sans Vert. du Bass. de Par., t.i, p. 823, pl. 64, figs. 17—20, 1860. 
Spec. Char. N. “ testdé minimd, ovato-trigond, turgidula, valdé inequilaterah ; posticé 
transversim truncata ; superné declivi; anticé attenuata, transversim tenui-sulcatd ; sulcrs 
antice paulo undulatis ; lunuld nullé; ano plano, non circumscripto ; cardine angusto, pauct 
dentato ; dentibus angustis distantibus ; fossuld minima, brevi, angustd ; marginibus sublente 
minutissime crenulatts.” —Desh. 
Shell small, ovately trigonular, slightly tumid, siphonal region short, obliquely trun- 
cated ; pedal region ovately rounded; concentrically ridged or sulcated ; ridges slightly 
irregular ; no lunule; anal region smooth, convex in the centre; dental margin narrow, 
teeth few and small; margins crenulated. 
Length, ‘th of an inch. 
Localities. Bracklesham (Edwards). 
France. Le Guépelle, Chéry-Chartreuve, Ver, Beauval, Houdan (Deshayes). 
The figure was taken from a unique and perfect specimen in the cabinet of Mr. 
Edwards. 
So far as I am able to determine from figure and description in the work above 
referred to, I think our little shell may be considered as identical with the Paris Basin 
