ARCA. ARK. 
7 
finally and across, and marked with a few transverse 
wrinkles ; under the skin whitish, yellowish, or dusky- 
brown, with angular zigzag chesnut or orange-yellow 
stripes or lines, which in the younger sheila are of a car¬ 
nation color, often spotted with red; inside white, with 
sometimes a purplish-brown tinge on one side, and marked 
with fine longitudinal lines which extend as far as the po¬ 
lished area round the margin: beaks quite central, promi¬ 
nent, not curved to either side nor quite close together at 
their points: teeth in a curved line, placed obliquely, about 
twelve on each side the beaks : diameter sometimes nearly 
three inches. 
Southern and western coasts, and Dublin bay. v. v. 
% Area Glycymeris. Large Ark . 
Lister, pk 240. f. 77 — Linn. Trans, viii. pi. 3. f. 3. 
Shell much resembling the last, but the sides are not 
quite equal, one of them being a little produced; in conse¬ 
quence the circumference is not exactly orbicular, nor the 
beaks quite central. 
Specimens of these two species, if they are really distinct, 
we have examined, from a quarter of an inch in diameter, 
to three inches and a half long, and three and a quarter 
wide. In the number of teeth, markings, and external 
coat they exactly correspond ; and we think we can per¬ 
ceive a gradual tendency to a deviation from their exact 
circular form as they enlarge to the fullest growth, and 
thus consequently causing the beaks to lose their central 
position, a circumstance by no means uncommon in many 
bivalve shells. If our conjecture should turn out eventually 
to be correct, the A. pilosa must be considered as the 
younger shell of A. Glycymeris, which latter is of very rare 
occurrence in these, climates. The finest and most perfect 
series which we have seen are in the cabinet of Mrs. Q. 
W. Loscombe of Exmouth, and were taken on the Dev?n 
and Cornish coasts, v. in. 
3. Area reticulata. Reticulated Ark. 
Lister, 233. f. 67. 
Area barbata. Bronm , JFern. Soc. pi. -4. f. 6. 
Shell oblong, somewhat rhombic, rather flat, strong, 
• J ’ white. 
