146 
CONCHIFERA. 
OSTREA. 
O. expansa. Sowerby, III. p. 65, pi. 238, fig. 1. 
Broad ; length and breadth nearly equal ; deltoidal, with 
obtuse angles; beaks obscure, hinge area wide, fiat; slightly 
elevated, and nearly straight; cicatrix broad, with a sinus at 
the beak; margin with largo undulations, surface laminar; 
muscular impressions very large aud deep. 
Portland Sand, Whitchurch ; Quainton, Buckinghamshire ; 
Wiltshire and Bedfordshire. 
12. Ostrea cndulata. —The Waved Oyster, pi. LVI1I. 
fig. 6. 
0. undulata . Sowerby, III. p. 65, pi. 238,* fig. 2. 
Subtriangular, recurved, convex, and rounded posteriorly; 
thick; beaks blunt; surface with many longitudinal depressed 
ribs, and shallow intervening furrows, with numerous distant, 
undulating, imbricated laminae ; cicatrix elongated, ovate, and 
oblique; hinge pit slightly elevated. 
Portland Sand, Yale of Wardour. 
13. Ostrea flabellula. —The Little Fan Oyster, pi. 
LV1L figs. 11, 12. 
O. flabellula . Sowerby, III. p. 97, pi. 253. 0. cymbula . 
Lamarck, An. San. Yert. YL pt. 2, p. 215. 0. ckama pli- 
cala. Brander, p. 36, pi. 7, fig. 84-, 85. Deshayes, pi. 63, 
figs. 5, 6, 7. 
External form very variable, oblong, and always subarcuated ; 
beaks prominent, that of the larger valve much curved ; larger 
valve deep, longitudinally and irregularly curved and plaited, 
with the margin dentated ; smaller valve fiat, smooth, with 
remote imbricated lamina ; margin plain; the lateral crenu- 
lations are well marked, on the sides and margin of the fiat 
valve Ufty^ke hinge. 
London Clay, Barton and Bracklcsham. 
14. Ostrea ten era. —The Tender Oyster, pi. LVII. fig. 14. 
O.+ tener. Sowerby, III. p. 95, pi. 252, figs. 2, 3. 
Much elongated, slightly curved, thin, depressed; beak of 
the upper valve acute, and included in the frequently curved 
beak of the under valve, and canaiiculated; surface almost 
plain and smooth, with obsolete imbricated laminae. 
Plastic Clay, Woolwich. * 
15. Ostrea Meajdii.—M eades Oyster, j»l.LYIII. fig. 3. 
O. Meadii. Sowerby, III. p. 95, pi. 252, figs. 1—4. 
Much elongated, thick; hinge area large, the pit wide; 
beaks projecting; attached valve very deep, and longitudin¬ 
ally rugged and undulated ; the other plain and flat, with 
lateral crenulations near the hinge ; odges very irregular. 
Great Oolite, Somersetshire. 
Hi. Ostrea gig ante a.— The Gigantic Oyster, pi. LVII. 
fig. 4. 
0. gigantea. Brander, p. 37, pi. 8, fig. 88. Sowerby, I. 
p. 143, pL 64. 
Slightly elongated, very thick, irregular in form, umbo 
short, very little incurved; hinge-pit large, tripartite, situ¬ 
ated upon a slightly oblique elevation, with its sides fiat and 
striated, and its internal end perpendicular to the surface of 
the valves, aud not gradually curved into the sides of the 
shell, as in other species. 
This shell is very large, frequently measuring upwards of seven and 
a half inches, and weighing two to three pounds. 
London Clay, Barton and Bognor. 
17. Ostrea pulciiua.—T he Fine Oyster, pi. LIX. fig. 12. 
0. pulchra . Sowerby, III. p. 141, pi. 279. 
Nearly orbicular, compressed ; one valve convex, with an 
obscure beak, and numerous radiating flat ribs and shallow 
furrows, crossed by wide-set undulating laminae; the other 
valve almost flat, with a short, blunted, slightly incurved 
beak; hinge-line parallel. 
Plastic Clay, Woolwich and Sundridge. 
18. Ostrea soutaria. —The Solitary Oyster, pi. LIX. 
figs. 8 and 11. 
0. solitaria. Sowerby, Y. p. 105, pi. 468, fig. 1. 0. pul - 
ligera . Gold fuss, pi. 72, fig. 11 ? 
Obovate, thick ; sometimes incurved; beaks short ; surface 
with many divergent strong and frequently furcated ribs, aud 
deep intervening furrows, crossed by elevated rugged imbri¬ 
cated lamime; one valve flatter than the other. 
Portland Stone, Dunton, Bucks; and the Coral Rag, 
Malton. 
19. Ostrea macuoptf.ua. —The Long Winged Oyster, 
pi. LYIII. figs. 1, 2. 
0. macroptera . Sowerby, Y. p. 105, pi. 468, figs. 2, 3. 
Parkinson, III. pi. 14, figs. 4. 
Falciform, compressed, with a large rectangular wing within 
the curve; surface with irregular, undulating, deep plaits; 
deeply furrowed and acutely ribbed towards the margin of 
the valves, producing a series of deep and sharp tooth-like 
processes, locking into each other; hinge area wide, triangu¬ 
lar, the pit for the ligament broad and much incurved; beaks 
long, incurved aud pointed. 
Gualt, Folkstone, and Lower Greensand, Atherfield and 
Berehead. 
20. Ostrea cauinata. —The Keeled Oyster, pi. LIX. 
fig. 6. 
0. carinata. Lamarck, YI. pt. I. p. 216, Ency. Moth, 
pi. 187, figs. 3, 4, 5. Goldfuss, Pet. pi. 74, fig. 6. Sowerby 
1Y. p. 89, pi. 365. 
Elongated, arcuated, irregular and much inflated, and point¬ 
ed at both extremities; sides flattened; whole surface with 
numerous transverse deep furrows, and strong elevated angu¬ 
lar sharp ribs; the centre with a keel; margin with strong 
deep tooth-like processes locking into each other. 
Chalk Marl, Dover and Lyme Regis; Upper Greensand, 
Chute Farm, and Southbourn ; Lower Greensand, Kent and 
Isle of Wight. 
21. Ostrea Marshii. — Marsh's Oyster, pi. LIX. 
fig. 10. 
0. Marshii . Sowerby, I. p. 103, pi. 48. Goldfuss, pi. 
73. O. diluviana. Parkinson, III. pi. 15, fig. 1. 
Longitudinal, oblique, compressed, beak obscure; obscurely 
eared, 7 or 8 angular, large, obliquely longitudinal ribs and 
furrows, crossed by concentric, zigzag, undulating lamina? ; edge 
thick, with strong and very deep-set triangular tooth-like 
processes locking into each other. 
Middle Oolite, Yorkshire and Wiltshire ; the Inferior Oolite, 
Yorkshire and Gloucestershire. 
22. Ostrea gregauia.— The Gregarious Oyster, pi. LVII. 
fig. 10. 
O. gregaria. Sowerhv, II., p. 19, pi. III. fig. 1. 
Clustered, oblong, generally curved ; substance of the shell 
thin, especially towards the edges; beaks long, very slightly 
