130 EOCENE MOLLUSCA. 
A single specimen from the above locality is in Mr. Edwards’s cabinet, and this I am 
unable satisfactorily to assign to any other species. I therefore give it the above name 
provisionally. The species this shell most nearly resembles is Z. od/ata, from Highgate, 
but the present shell is thinner and flatter; it is also comparatively longer, and the 
siphoni-lateral margin is more pointed. Our shell appears to be quite smooth upon the 
exterior, and glossy; the dorsal margin on the pedal side is slightly convex; on the 
siphonal side it is nearly straight. The specimen is firmly imbedded in the matrix. 
9. Lupa susstriata, Morris. Tab. XVII, fig. 5. 
Lepa susstriaTa. Morris. Geol. Journ., vol. viii, p. 266, pl. 16, fig. 7, 1852. 
Spec. Char. L. testé minima, ovato-elongatd, subtrigond, tumidiusculd, sub-inequ- 
laterali, concentricé striatd aut obtusé costatd ; pedi-regione ovato-rotundatd ; siphoni- 
regione longiore, subrostratd et sublevigatd ; umbonibus prominulis ; lunuld via distineta ; 
ano elongato, lanceolato. 
Shell small, ovately elongate, obtusely trigonular, rather tumid, slightly inequilateral ; 
concentrically striated or obtusely ridged; pedilateral margin ovately rounded; siphoni- 
lateral obtusely pointed ; beaks prominent; Iunule ill defined. 
Length, *ths of an inch; height, + of an inch nearly. 
Locality. Richborough (Prestwich), Pegwell Bay (Hdwards). 
“This shell, collected by Mr. Prestwich from the Thanet sands at Richborough, 
Castle and Pegwell Bay, is difficult to distinguish from Wweula striata, Lam., which it 
resembles in general form, but is rather longer in a transverse direction, and the strize 
differ a little, and are interrupted towards the posterior margin in some of the specimens 
examined.” — Morris. 
In addition to the above remarks I may observe, that the French shell has different 
proportions: the siphonal region is rather less than the pedal, whereas in the British shell 
it is the reverse. ‘This species appears still more to differ from Leda minima, which has a 
distinct and well-marked anal or corselet region, with a defined and prominent ridge, 
and the siphoni-lateral margin is in that shell more pointed than in either our present 
species or the French shell Z. striata. 
UNIO. Phillippson, 1788. 
Generic Character. Shell equivalve, inequilateral, generally thick and externally 
smooth, occasionally corrugated or ornamented with nodules or spines; aged specimens 
sometimes become ponderous. Covered by an epidermis in the living state; eroded at 
the umbones; hinge with two short cardinal teeth in the left valve, and one, sometimes 
two, in the right, and one elongated lateral tooth beneath the dorsal margin. Impressions 
