OsTRACEA. | 
duced in the middle; whole surface invested with fine longitu- 
dinal, divergent strie; perforation a little triangular. Length 
nearly an inch and a quarter; breadth one inch. 
This specimen was cast ashore at Teignmouth. 
It is doubtful whether this is a true British species. 
Genus 2.—OrpicuLa.—Cuvier. 
Shell inequivalve, nearly orbicular, compressed; generally 
irregular in form, adherent, flat, and attached by means of a 
fibrous substance, passing through an orifice near the centre of 
the lower valve; upper valve patelliform, its vertex posterior, 
or nearly central; each valve provided with four muscular im- 
pressions, two of which are large, approximate, and situate near 
the centre, and two smaller and more distant, placed near the 
posterior margin; those of the lower valve not so well defined 
as the others; contiguous to the inner extremity of the orifice 
there is an obtuse testaceous process; destitute of hinge teeth, 
or a ligament. 
1. Orsicuta Norvecica, pl. XXII, f. 9, and pl. XX, f. 
21,.22. 
Orbicula Norvegica, First Ed., pl. 37, f. 21, 22, and pl. 34, 
f. 9; Lamarck, VI, pt. Ist, p. 242, G. B.; Sowerby, Linn. 
Trans., XILI, p. 468, pl. 26, f. 2; Stark, Elem. Nat. Hist., II, 
p- 75; Discina Ostreoides, Lamarck, VI, pt. Ist, p. 237; 
Fleming, Brit. An., p. 376; Stark, Elem. Nat. Hist., p. 76; 
Turton, Brit. Biv., p. 238; Patella anomala, Miiller, Zool. 
Dun., I, p. 14, pl. 5, f. 1 to 7; Patella distorta, Fleming, 
Edin. Ency., VII, p. 65, pl. 204, f.4; Montagu, Linn. Trans., 
XI, p. 195, pl. 13, f. 5. 
Shell subquadrangular, somewhat irregular in shape, and 
rugged in the margin; upper valve patelliform, convex, con- 
centrically wrinkled by the lines of growth, with a wart-like 
subcentral protuberance; of a dull yellowish-brown colour ; 
under valve quite flat, very thin, and adhering its whole cir- 
cumference to submarine stones, and other substances; inside 
bluish-white, and minutely granulated; furnished with four 
muscular impressions. 
Found in deep water at Zetland, and is not uncommon in the 
Clyde, particularly in Rothesay Bay. 
Famity II.—Osrtraceka. 
Ligament placed either interiorly, or nearly so; shell irregu- 
lar in form, foliaceous, and sometimes papyraceous. 
Sus-Diviston I—Ligament placed interiorly; shell thin, 
papyraceous. 
Genus 3.—ANnomiA.—Linneus. 
Shell inequivalye, irregular, operculated; under valve flat- 
tened, with a large circular or ovate perforation near the hinge, 
with its edges turned back, through which protrudes a testace- 
ous, or bony, straight, elliptical operculum or plug, with a dilated 
base, by which the shell adheres to extraneous bodies; upper 
valve the larger, concave, and entire; ligament large, transverse, 
internal, and placed within the upper valve, at the umbo, and 
to a prominent, expanding appendage in the depressed valve; 
lower valve with a single, orbicular, nearly central, muscular 
s 
MOLLUSCA. 69 
impression; upper valve .with three impressions, situate con- 
tiguous to each other, the largest is next the base of the shell, 
which is connected by means of its muscle with the plug, and 
the other two are also connected, by the medium of their 
muscle, with the single impression in the lower, or flattened 
valve. 
1. Awnomi1a Epuippium, pl. XXII, f. 1 and 4. 
Anomia Ephippium, First Ed., pl. 34, f. 1 and 4; Linné, p- 
1150; Lamarck, VI, pt. Ist, p. 226; Pennant, p. 109, pl. 62; 
Montagu, p. 155; Donovan, I, pl. 26; Maton and Rackett, p. 
102; Brown, Ency. Brit., p. 422; Ib., Ency. Edin., p. 548, pl. 
54, f. 3; Ib., Wernerian Mem., p. 514; Fleming, p. 395; Ib., 
Edin. Ency., p. 98; Forbes, p. 38; Turton, Biy., p- 227, pl. 18, 
fo 23: 
Shell suborbicular, subpellucid, irregularly waved and wrin- 
kled; generally of a pale yellowish-white on the outside, and of 
a shining pearly lustre within, reflecting various hues, according 
to the play of light; one valve convex, the other flat, with a 
pretty large perforation near the hinge, through which protrudes 
a thick testaceous plug, by which the shell is affixed to extrane- 
ous bodies. 
This species is not uncommon in our seas, attached to oysters 
and other extraneous bodies; often assuming the form of the 
substance to which it is attached. Very curious specimens are 
frequently found adhering to the Pecten opercularis and Pecten 
maximus ; these take the impression of the ribs and markings 
of those species, and produce a very beautiful appearance. 
The A. Ephippium abounds in Lough Strangford, Ireland, 
of a very large size, adhering to Oysters. 
2. ANOMIA UNDULATA, pl. XXII, f. 2, 3. 
Anomia undulata, First Ed., pl. 34, f. 2, 3; Linn. Gmelin, 
p- 3346; Montagu, p. 157 and p- 580, pl. 4, f. 6; Ency. Meth., 
pl. 184, f.5, 6; Maton and Rackett, p: 103; Fleming, Brit. 
An., p- 395; Ib., Edin. Ency., p- 98; Brown, Ency. Brit., p. 
422, pl. 153, f.9; Ib., Wernerian Mem., p- 514; Ib., Conch. 
Text Book, p. 110, pl. 14, f.2; Forbes, p- 39; Turton, Brit. 
Biv., p. 230; Ostrea striata, Da Costa, p- 162, pl. 11, f. 4; 
Donoyan, pl. 45. 
Shell strong, flat, sometimes thin, and pellucid; generally of 
a suborbicular, or slightly elongated form; external surface with 
numerous, stroug, rib-like striz, emanating at the small, pointed, 
flattened umbo, which is placed a little within the margin, and 
radiating towards the sides and base of the shell, which is gene- 
rally slightly crenulated; upper valve a little rounded; lower 
valve flat, with a very large, oblong-ovate perforation, destined 
for the passage of a testaceons plug, by which the animals 
adhere to marine bodies, on one side of which is a triangular 
concave space, finely striate; outside dirty green; inside almost 
always of a clear glossy green, which is more intense towards 
the centre; margin of a bluish, iridescent hue; the plug ter- 
minates in a thin oval layer, strongly striated transversely, and 
crossed by fine longitudinal lines. 
Found on stones, shells, &c., within low water-mark, on many 
of our shores; we may particularise South Devon, Saleomb Bay, 
rocks at Torbay, the Frith of Forth; Callina Bay and Rathgar- 
mont, Lough Strangford, Ireland. 
3. ANomia squamuLa, pl. XXII, f. 5. 
Anomia squamula, First Ed., pl. 34, f. 5; Pennant, p- 109, 
No. 71; Da Costa, p. 167; Montagu, p. 156 and p. 561; 
