105 
MYA. GAPER. 
striate, perlaceous within: beaks nearer one end: binge 
with a broad notched tooth in both valves, and two lateral I 
plates in one valve and one in the other, all locking into l 
one another: length sometimes nearly two inches, and four 
in breadth. 
It differs from the next, in having both the ends rounded, 
and the beaks less prominent. 
In the river Kennet: rare. v. v . 
■ 20. MyaPictorum. Painters Gaper. 
Lister, pi. 147- f. 3— Da Costa, pi. 15. f. 4 — Pennant, 
pi. 45. f. 1— Wood, pi. 19. f. 3,4— Dorset Cat. pi. 12. f. 4. 
Mya ovalis* Donovan , pi. 89. 
Shell oblong-oval, produced and narrower at one end, 
covered with a dark green skin, which in old shells becomes 
nearly black, irregularly striate transversely, perlaceous ( 
within ; when shut the valves are closed in front, but a little 
open at both ends : teeth as in the last species, and of 
about the same size. 
Rapid rivers : rare. v. v. 
21. Mya ovata. Oval Gaper. 
Lister, pi. 147* f. 2— Wood, pi. 19. f. 5— Donovan, 
pi. 101, and 122. 
Shell oval, very convex, thick and brittle, mbch round¬ 
ed at one end, produced and very narrotv at "the other, ir¬ 
regularly and coarsely wrinkled transversely, with some¬ 
times faint longitudinal rays, covered .with a green skin 
which varies more or less to a dark-brown towards the 
margin, under which it is of a fine opalaceous white color; 
inside perlaceous : beaks rather prominent; teeth as in the 
two last, and nearly the same size ; but it is narrower than 
M. Batava, and broader than M. Pictorum. 
In rapid rivers, v. v. 
22. Mya margaritifera. Pearl Gaper , Fig. 47. 
Lister, pi. 149. f. 4— Pennant, pi. 46. f. 2— Pa Costa, 
pi. 15. f. 3— Donovan, pi. 73— Wood, pi. 23. f. 1 to 3. 
Shell oblong-oval, thick, strong, covered with a black- 
brown 3kin, rounded at one end and a little angular at the 
other where it is sloping and depressed from the beaks to 
the 
