42 EOCENE MOLLUSCA. 



trie striae or small imbrications. The auricles are nearly equal, and they are ornamented 

 with eight or ten moderately sized rays. 



7 Pecten Prestwichii, Morris. Tab. VIII, fig. 7, a, b. 



Pecten Prestwichii. Morris. Geol. Journ., vol. viii, p. 26C, t. 1G, fig. 8 a, b, 1852. 



— — Id. Cat. Brit. Foss., p. 178, 1854. 



— — Desk. An. sans Vert, du Bas. de Par., p. 75, pi. 79, figs. 4 — 6. 



— breviauritus? Id. - - - p. 74, - 1 — 3. 



Sjjec. Char. " P. testa, tenui, compressd, radiatim obsolete costatd, costis subsquamosis, 

 Interstitiis oblique irregulariter striatis ; auriculis inaqualibus, 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 costae." 



Diameter, 1 inch. 



Localities. Richborough Castle {Prestwich), Heme 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 striae ; these are most conspi- 

 cuous as they approach the pedi- and siphoni-lateral margins ; 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 striae 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. breviauritus, 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. 



S. Pecten reconditus, Solander. Tab. IX, fig. 3, a — d. 



Ostrea recondita. Solander. Brand. Foss. Hant., p. 42, pi. 8, fig. 107, 17GG. 

 Pecten reconditus. Nyst. Coq. Foss. Belg., p. 302, pi. 25, fig. 2 a, b, 1843. 



— — J. Sow. in Dixon's Geol. of Suss., t. 3, fig. 27, 1850. non. Sow. Min. 



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. 



