6 ArcA. ark. 
pression roughened by two or three slight longitudinal , 
ridges, and in the smaller valve forming a raised transverse i 
ridge, which is grooved along the middle, and reflecting at 
tin?sides for the purpose of receiving the processes ot the 
opposite valve, with two small reflected tooth-like projec¬ 
tions near the middle of the shell, and a small erect one at 
the base of each: length about an inch ; breadth seven- 
eighths of an inch. 
Found by Mr. Fleming in the Shetland Islands: very rare. 
10. Anomia cylindrica. Cylindrical Boat-shell. 
Anoraia cymbiformis. Linn. Tram. viii. pi. 3. f. 6. ^ I 
Shell oblong-oval, thin, semitransparent, brownish-1 
white, strongly wrinkled or striate transversely, the wnn-i 
kies often rising into thin membranaceous scales which 
turn downwards and are nearly incumbent on each other; | 
the upper-valve convex, more or less cylindrical according, 
CffC ' % t0 tilc substances on which it is fixed, narrowed towards the 
top, tumid and turned in at the beak over the under valve, 
which is flat and perforated near the top; inside glossy- 
white : length nearly half an inch; breadth about a third, 
of its length. 
We find this shell frequently on the Devonshire coast, 
attached to Fuci, consequently of a less cylindrical form j 
than when it adheres to Sertularice, or the spines of the 
Echinus, v. v. 
ARCA. ARK. 
Shell of two equal valves : hinge with numerous 
teeth, alternately locking within each other. 
A. JVtth the margin notched. 1, to.4- 
B. With the margin very entire. 5, to ll. 
I. Area pilosa. Downy Ark. 
Lister , pi. 247-f- 82—Pennant, pi. 61. f. 1—Z>» Cuto, 
pi. 11. f. 2—Dorset Cat. pi. 11. f. 2 —Linn. Trans, n 
pi. 18. f. 1,2, and viii. pi. 3. f. 4. 
Area Glycymeris. Donovan , pi. 37- 
Shell thick, convex, with the sides exactly equal or rardy 
a little flexuous on one side, covered with a dark-brbva' 
downy skin, particularly round the margin, with obsccre I 
- broad rounded remote ribs, minutely striate both longitu¬ 
dinally f 
