BIVALVIA. 31 
19. Osrrea taBuLata, J. Sowerby. Tab. IV, fig. 1, a, 6d. 
OstreA TABULATA. J. Sow., in Dixon’s Foss. of Suss., pp. 117, 226, 1850. 
— — Morris, Catal. Brit. Foss., p. 175, 1854. 
Spec. Char. Testa orbiculatd, depressd ; levigatd ; valvd inferiore imbricatd obscuré 
radiata ; valvd superiore pland, nitidd, politd ; umbonibus parvis. 
“Shell orbicular, depressed, smooth ; upper valve slightly concave, even, its plates few, 
with distant, scarcely raised edges ; lower valve obscurely marked by radiating undulations, 
its plates few, in groups, with remote, deeply imbricating edges; beaks small, pointed ; 
muscular impression ovate, curved, of a moderate size.”—Sowerby. 
Diameter, 7 inches, 
Locality. Bognor. 
This is an abundant shell at Bognor, to which locality it appears to be restricted. 
Mr. Sowerby remarks “that it was evidently a rapid growing shell; its nearly smooth 
external laminee extend far between each period of growth, and show their fibrous 
structure distinctly, especially upon the surface.’ The specimens generally have 
adhered only in the young state by a very small portion of the surface, and are 
solitary. I have rarely seen them in groups. A specimen in Mr. Wetherell’s 
cabinet shows the muscle-mark to be rather elongate, and more curved than is the rounded 
form of this mark in gigantea. The lower valve in the young state is obscurely rayed, 
and the upper is generally glossy, and the shell is flatter or more compressed than that of 
gigantea. 
20. Osrrra teNERA, J. Sowerby. ‘Tab. VI, fig. 1, a, 2. 
OstreA TENER. J. Sow. Min. Conch, t. 252, figs. 2, 3, 1819. 
— enperA. Jd., in Dixon’s Foss. of Suss., p. 174, t. iv, figs. 2, 3, 1850. 
— — D' Orbigny. Prod. de Palzont., t. li, p. 307, No. 199, 1850. 
— — Morris. Catal. Brit. Foss., p. 175, 1857. 
Spec. Char. Testa elongatd, attenuatd, angustd, depressd valvd inferiore sub-pland, 
transversim lamellosd, valvd superiore striatd vel inornatd ; umbonibus longis attenuatis ; 
Sossuld ligamenti angustd. 
Shell elongate, attenuated, depressed ; lower valve very slightly convex and transversely 
lamellated ; upper valve flat, striated, or plain ; umbones attenuated, ligamental ; area long 
and pointed. 
Height, 4 inches. 
Localities. Woolwich, Sundridge Park, New Cross, smooth and thick var. (Prestwich ). 
Bracklesham, thin and striated var. (dwards). : 
