ARCA. ARK. 7 



d'mally 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 shells 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. 



2. Area Glycymeris. Large Ark. 



Lister, pi. 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. C. 

 \V. Loscombe of Exmouth, and were taken on the Devqn 

 arid Cornish coasts, v. m. 



3. Area reticulata. Reticulated Ark. 

 Lister, pi. 233. f. 6/. 



Area barbata. Brown, Wern. Soc. p!. 24. f. 3. 



jSbell oblong, somewhat rhombic, rather $at, strong-, 



