OSTREA. 
CONCHIFERA. 
145 
od divergent stria); umbo flat; part of the sides slightly crenn- 
lated ; perforation very large. 
Pleistoceno Marine Formation, Ayr and Suffolk Crag. 
8. Anomia radiata.— The Rayed Anomia, pi. LXVI.* 
fig. 22. 
A. radiata . Sowerby, Geo. Trans. 2d Ser. IV. p. 338, 
pi. 4, fig. 5. 
Flat, irregularly orbicular, with fine radiating striae. 
Lower Greensand, Sandgate. 
9. Anomia squamula. —The Scaled Anomia, pi. LVII.* 
fig. 10. 
A . squamula. Brown, Illust. Rec. Conch. Brit. p. 09, 
pi. 22, fig. 5. 
Suborbicular, very thin and flat, with indistinct concentric 
wrinkles. 
Pleistoceno Marine Formation, Ireland, and Coral Crag, 
Malton. 
Genus XVII.—OSTREA. — Linnaeus . 
Shell inequivalve, irregular, and foliaceous ; umbones somo- 
wliat separated, and of unequal size; lower valve largest, 
concave, and often adherent; upper valve smallest, and some¬ 
what plain ; hinge destitute of teeth, but sometimes slightly 
crenated on tho anterior side near the beaks ; ligament partly 
external; tho facet to which it is attached subtrigonal and 
tripartite, and divided by two elevated lines which divaricate 
from tho umbo; each valve provided with two muscular im¬ 
pressions, tho one largo, suborbicular, and nearly central; 
the other very small and situate near tho hinge. 
1 . Ostrea acuminata. — The Acuminatod Oyster, pi. 
LVII. fig. 2, 3. 
0. acuminata. Sowerby, II. p. 81, pi. 35, figs. 2, 3. 
Much elongated, depressed, and incurved; upper valve a 
little concave, and rather smooth ; distinctly eared, and with 
rather acute umbones; base acuminated; surface with largo 
subimbricated transverse undulating lamina). 
Fuller's Earth, Bathford Hill, Great Oolite, Stonesfield 
and Cain’s Cross; Inferior Oolite, Limpley Stoke. 
2. Ostrea canaliculata. —The Canaled Oyster, pi. 
LVII. fig. 9. 
0. canaliculata. Sowerby, II. p. 81, pi. 35, fig. 1. 
Depressed, much elongated, curved, slightly and equally 
eared ; one or two descending sinuses in the anterior margin 
near the base; sides almost parallel, posterior side fequently 
gaping; near tho beak a few concentric laminae, and two or 
more canaliculated projections in tho lower valve, which is 
more convex than the other; upper valve flat. 
Upper Chalk, Lewes and Norwich. 
3. Ostrea Bellovacina. —The Bellovian Oyster, pi. 
LVII. fig. 1. 
0. Belovacina. Lamarck, An. du Mus. VIII. pi. 159, 
and XIV. pi. 20, fig. l.^Deshayes, Coq. Fos. pi. 48, fig. 12. 
Ib. Ann. San. Vert. VI. pt. 1, p. 228. Sowerby, IV. p. 121, 
pi. 388, figs. 1, 2. 
Oblong; form irregular, somewhat orbicular or wedge-shap¬ 
ed, thick; lower valve convex, composed of undulating, sub¬ 
imbricated lamina); beak considerably produced, and straight 
on each side; ligamental area, a little elevated above the sur¬ 
face of the shell; in the hollow valve it is curved and acute, 
with a deep canal in the middle. 
Plastic Clay, Phumstead, Woolwich, Reading, Headley, &c. 
4. Ostrea edulina. —The Small Edible Oyster, pi. LVII. 
fig. 15. 
0. edulina. Lamarck, An. San. Vert. VI. pt. 1, p. 218. 
Sowerby, IV. p. 122, pi. 388, figs. 3, 4. 
Suborbicular, or subovate ; moderately thick; lower valve 
convex, composed of undulating laminae ; upper valve very 
smooth anil depressed ; beak curved and pointed; but desti¬ 
tute of straight lines on its sides. 
Plastic Clay, Charlton and New Cross. 
5. Ostrea ueviuscula. —Tho Very Smooth Oyster, pi 
LVII. fig 13. 
0. lawiuscula. Sowerby, V. p. 143, pi. 488, fig. 1. 
Depressed, rounded, or somewhat triangular, beak subacuto 
and retroflected ; scales distant; surface smooth and obscurely 
imbricated ; lower valve destitute of ribs. 
Kimmcridge Clay, Aylesbury and Bedford. 
C. Ostrea costata. —The Ribbed Oyster, pi. LVIII. fig. 9. 
0. costata. Sow’erby, V. p. 143, j>1. 488, fig. 3. 
Suborbicular, low r er valve with numerous furcated and 
doubly furcated divergent ribs; upper valve flat, with an 
undulated margin; beak obscure. 
Great Oolite, Hampton and Ancliff. 
7. Ostrea obsccr a. —The Obscure Oyster, pl.LIX. figs. 3, 4. 
Sowerby, V. p. 143, pi. 488, fig. 2. 
Oblong; irregular; beak obtuse and curved; hinge area 
large, triangular; lower valve very deep, tho other flat. 
Great Oolite, Ancliff, Wiltshire. 
8. Ostrea dorsata. —The Backed Oyster, pi. LIX. fig. 2. 
0. dorsata. Sowerby, V. p. 144, pi. 489, figs. 1,2. Des- 
hayos, Coq. Fos. I. pi. 53, figs. 9, 10, 11, and pi. 64, figs. I, 
2, 3, 4. 
Oblong ; form variable ,* convex ; beaks blunt; upper valve 
very convex, with numerous longitudinal subimbricated, many- 
branched striae ; inuer margin toothed. 
London Clay, Barton. 
9. Ostrea semiplana. —The Half-plain Oyster, pi. LIX 
fig. 7. 
O. semiplana. Sowerby, V. p. 144, pi. 489, fig. 3, Man- 
till, Geo. Suss. p. 207, pi. 25, fig. 4. 
Oval; depressed ; surface largely foliated ; valves flat in the 
middle ; edges free from deep sinuations. 
Upper Chalk, Gravesend, Lewes, and Wiltshire. 
10. Ostrea deltoidea. —The Deltoidal Oyster, pi. LIX. 
fig. 10. 
O. deltoidea. Lamarck, Env. de Paris, p. 265. Sowerby. 
IV. p. Ill, pi. 148. 
Equivalve, thin, flat, much compressed, triangular ; laminar ; 
beaks equal, much produced, and straight, and pointing on 
ono side; one side with a deep sinus ; edges extending con¬ 
siderably beyond the enamelled surface of the interior, giving 
the external contour a more rounded aspect than the internal. 
Kimmcridge Clay, Portland, Weymouth, and counties of 
Buckingham, Bedford, and York. 
11. Ostrea exp ansa. —The Expanded Oyster, pi. LVIII. 
fig. 7. 
