42 EOCENE MOLLUSCA. 
tric striee or small imbrications. The auricles are nearly equal, and they are ornamented 
with eight or ten moderately sized rays. 
7. Pecren Prestwicuu, Morris. Tab. VIII, fig. 7, a, 6. 
Prcten Prestwicuit. Morris. Geol. Journ., vol. viii, p. 266, t. 16, fig. S a, 6, 1852. 
— — Id. Cat. Brit. Foss., p. 178, 1854. 
= — Desh. An. sans Vert. du Bas. de Par., p. 75, pl. 79, figs. 4—6. 
—  BReEviAuritus? Id. - - - - p- 74, - 1—3. 
Spec. Char. “P. testd tenui, compressa, radiatim obsolete costatd, costis subsquamosis, 
interstitiis oblique irregulariter striatis ; auriculis inequalibus, radiatis.” 
“ Shell thin, compressed ; margin orbicular, with a rectangular beak ; radiated with very 
slightly raised ribs, distinctly imbricated, the intervening furrows twice as large as the 
ribs ; irregularly and obliquely striated ; ears unequal, with three or four radiated coste.” 
Diameter, 1 inch. 
Localities. Richborough Castle (Prestwich), Herne Bay (Bowerbank). 
This species possesses about sixty small ribs or rays, very slightly elevated, and the 
surface is covered with diverging or divaricating and curved striz; these are most conspi- 
cuous as they approach the pedi- and siphoni-lateral margims; the auricles are compara- 
tively large, unequal in size, with a small sinus at the base of the right one; these 
auricles are covered with about five or six rays. The diverging stria appear to cover 
our shell, passing over the riblets, as well as between them; and there appears to be 
a large muscle-mark under the pedal auricle. I have seen only two specimens. 
The British fossil corresponds so closely with the older species, P. dreviauritus, that, 
judging alone from figure and description, I am unable to detect any difference which can 
fairly be called specific ; and unless there be greater distinction shown between specimens 
when compared, the name of our species will have to be changed. In the figure given in 
the ‘Geol. Journ.,’ above referred to, the artist has reversed the auricles. 
8. Prcren ruconpitus, Solander. Tab. IX, fig. 3, a—d. 
OstREA RECONDITA. Solander. Brand. Foss. Hant., p. 42, pl. 8, fig. 107, 1766. 
PrcrEn rEconpitus. Myst. Coq. Foss. Belg., p. 302, pl. 25, fig. 2 a, 6, 1843. 
= = J. Sow. in Dixon’s Geol. of Suss., t. 3, fig. 2 
Conch., t. 575, figs. 5, 6. 
= — Lyell. Belg. Tert., loc. cit. ant. p. 353, 1852. 
— —_ Morris. Cat. Brit. Foss., p. 179, 1854. 
— PLEBEIUS. Tennant. Strat. List. Brit. Foss., p. 31, 1847. 
7, 1850. non. Sow. Min. 
