116 MOLLUSCA FROM THE CRAG. 
in my Catalogue. The shell is very thin, and in the living state was no doubt nearly 
transparent, it has a prominent umbo, sloping towards each extremity, and is rounded 
there, while the ventral margin is quite straight, even inclining a little inwards in 
some specimens, and is deep or tumid, particularly at the upper part; the hinge is 
furnished with two teeth in each valve, diverging from the ligamental area, but do 
not extend far towards the sides, and in the left valve immediately beneath the umbo, 
and before the ligament, is a small cardinal tooth, but not one in the right valve; in 
perfect specimens the shell is beautifully glossy, and the exterior possesses a sort of 
irregular concentric striz, which I imagine is not its original appearance, and that 
probably it was ornamented in its recent state with more elaborate sculpture. 
3. LEPTON DEPRESSUM, JVyst. Tab. XI, fig. 6. 
Cycias? prpressa. Myst. Rech. Coq. Foss. d’Anv., p. 36, pl. 5, figs. 5, 6, 1836. 
ERYCINA DEPRESSA. Mysé. Coq. Foss. de Belg., p. 88, pl. 4, fig. 5, a, a, 6, ¢, e, 1844. 
Spec. Char. Testa transversd, ovatd, inequilaterali, depressd, tenui ; dente cardinali 
unico, dentibus lateralibus obtusis. 
Shell transversely ovate, slightly inequilateral, depressed and thin: hinge with one 
cardinal, and two obtuse lateral teeth. 
Length, { of an inch. 
Locality. Cor. Crag, Sutton. 
A single specimen of this shell in my Cabinet seems to correspond with what M. Nyst 
considers, probably with better materials than I possess, to be a distinct species, and 
the form certainly is different from that of any other already described; and as I am 
not imposing a new name, it will at least serve to call the attention of Collectors to 
its existence for better examination. 
My specimen may be thus more particularly described. One side is rather broader 
or deeper than the other, the longer side being the more narrow, and slightly pointed, 
the hinge teeth are very obtuse, perhaps not quite perfect, dorsal area truncate, with 
a depressed umbo: lateral teeth not very distant, two ovate muscular impressions 
rather deep, and a continuous line formed by the mantle. The exterior is somewhat 
rough and eroded, but appears as if it once had a more regular ornament. M. Nyst 
says of his shell: “Transversim subtilissimé irregulariterque striata,” and that it is 
in Belgium also a rare species. 
4. LepToN nitTIpuM, Turton. Tab. XI, fig. 7. 
Lerron nitrpum. Turt. Brit. Biv., p. 63, 1822. 
— — Flem. Brit. An., p. 429, 1828. 
— — S. Wood. Catalogue, 1840. 
— — Thorpe. Brit. Mar. Conch., p. 49, 1844. 
— Maegill. Moll. Aberdeen, p. 278, 1843. 
Ketura nivipa. Ford. and Hani. Hist. Brit. Moll., vol. ii, p. 92, pl. 36, figs. 3, 4, 1849. 
