110 EOCENE MOLLUSCA. 
truncated ; the slope filled by a large, pointed, nearly flat lunette, edge toothed ; impression 
of the abductor muscles shallow.” —(/. Sowerby). 
Length, \ inch ; height, $ths of an inch. 
Localities. Highgate, Potter’s Bar (Wetherell); Haverstock Hill (Zdwards). 
This species was apparently covered by a thick epidermis, and the umbones have been 
very much eroded. ‘The anal region or corselet is well marked and flat, with a slight rise 
in the centre, and covered only by lines of growth. The surface of the shell is smooth to 
the unassisted eye, but it is covered with narrow, deep, radiating lines, making the rays 
broad and flat, and there is a depression on the dorsal portion of the pedal region irre- 
spective of the lanceolated lunule, as if the ventral margins were capable of being widely 
separated. The species appears to be confined to the London Basin. 
The interior cast of a shell of this genus is figured and described in the ‘Trans. of 
the Geol. Soc.,’ 2nd series, vol. v, pl. 24, fig. 5, under the name WV. Badoensis, and is 
said by the author to “nearly resemble VV. Bowerbankii, but not truncated or pointed 
below the lunette.” This specimen came from Baboo Hill in Cutch, and it is in that 
easterly direction that we might look, I think, for shells probably identical with some 
of our own Eocene fossils, but I fear it is not possible to certify a species by the cast alone. 
There is also the cast of a species in this genus found in the Eocene Formation, between 
Holyport and Birfield; the specimen was deposited in the Museum of the Geological 
Society, by the late Mr. Warburton (marked No. 17839), and has a somewhat similar 
form, but it presents the same difficulty for determination, and I am unable to assign 
it to any species; these various casts do not show whether the inner margins were 
furnished with crenulations. 
4. Nucuxa carpioiwEs, Ldwards, MS. Tab. XIX, fig. 8. 
A single specimen from Pegwell Bay, in the cabinet of Mr. Edwards, has the above 
name attached to it, and it appears to belong to a distinct species; but it is very imper- 
fectly preserved, and I am unable to describe its true characters. The shell is externally 
rayed with distinct and well-marked striz or riblets, and the inner margin is crenulated. 
Its present name must be considered provisional. 
5. Nucuna compressa, J. Sowerby. Tab. XIX, fig. 5. 
Nucua compressa. J. Sow. Geol. Trans., vol. v, 2nd ser., p. 136, pl. 8, fig. 14, 1834. 
— _ Prestwich. Geol. Journ., 1847, p. 405. 
— _— Morris.» Catal. Brit. Foss., p. 217, 1854. 
