120 EOCENE MOLLUSCA. 
region, and it is comparatively shorter. The shell is thin, and there is no perceptible or 
distinct lunule on the pedal region ; neither is there any distinct corselet. The specimens, 
which are few in number, adhere firmly to the matrix, and I am unable to see the 
interior. 
20. Nucuna suprransversa, JVyst.? Tab. XIX, fig. 13. 
Nucuxa suptransversa. Nyst.? Coq. Foss. Belg., p. 227, pl. xviii, fig. 7, a, 6, 1844. 
—  oVATa. Id.? Rech. Cog. Foss. de Hoesselt et Kl. Sp., p. 13, No. 31, 
1836. 
— — Potiers et Mich.? Catal. de Moll. de Douai, t. ii, p. 120, No. 3, 1844. 
Spee. Char. N. testa transversd, oblongo-ovatd, turgidd, valde inequilaterali, obsolete 
radiata; «pedi-regione prelongd, paulo attenuatd; margine dorsali subrectd ; margine 
ventrali convewiusculd ; lunuld inconspicud ; ano ovato, in medio prominent ; marginibus 
crenulatis. 
Shell transverse or elongate, ovately oblong, or obtusely wedge-shaped ; very inequi- 
lateral ; obsoletely radiated; pedilateral margin slightly pointed ; dorsal margin nearly 
straight ; ventral margin gently curved; corselet ‘or anal region ovate, elevated in the 
middle ; margins crenulated. 
Length, ths of an inch ; height, jths of an inch. 
Locality. White Cliff Bay (/%sher). 
‘he specimen figured enriches the cabinet of Mr. Fisher, who tells me it is not rare, 
but very difficult to obtain in any degree of perfection. 
I have considered it as identical with the Belgian species, depending entirely for so doing 
upon figure and description, although the proportions given by M. Nyst do not quite accord 
with those of our own shell. This is extremely transverse or elongate—more so than any other 
species from the English Hocene deposits ; and the umbo, which is depressed and much 
eroded, is at the extremity of the shell, the siphoni-lateral margin forming almost a right 
angle with the dorsal edge. ‘lhe outer surface shows distinct but irregular lines of 
increase, and the nearly obsolete rays upon the specimen are most visible towards the 
pedilateral margin, as they are described to exist on the Belgian shell. : 
M. Nyst points out a distinction which exists between his shell and the one which he 
considers to be the same from the Paris Basin in the number of the hinge-teeth. Unfor- 
tunately | am unable to ascertain the dental characters of our shell. 
