MACTRA. 83 
between them; the lateral ones depressed: length two 
lines; breadth three. 
The internal toothed margin distinguishes this species 
from all its tribe. 
Devonshire coast: very rare. v. m, 
f 9. MactraListen. Listers Mactra. 
Litter, pi. 253. f. 88— Da Costa , pi. 13. f. 1 — Dorset Cat. 
Tellina plana. Donovan , pi. 64. f. 1. 
Shell oval-oblong, slightly triangular, thin, flat, semi¬ 
transparent, not polished, finely wrinkled transversely, 
somewhat sloping to the cartilage edge where it gapes a 
little: color pale russet-brown, sometimes dirty white, 
blueish, or inclining to black, often marked with transverse 
bands; inside smooth, white, glossy, with a plain margin: 
beaks small, central; hinge with a large triangular cavity; 
tbe primary teeth small, a single one in one valve locking 
1 into a cloven one in the other; lateral teeth none: length 
about an inch and a half ; breadth nearly two inches. 
Whether the M. Listeri and M. piperata of Gmelin be in¬ 
dividually the same, as Mr. Dillwyn supposes, we are un¬ 
able to determine ; but have chosen to retain the former 
denomination, as being so well known and so unexception¬ 
able appropriate, in preference to the uncouth name adopt¬ 
ed by Mr. Dillwyn from M. Poiret, whose Travels he has 
quoted, but not admitted into his catalogue of authors. 
At the mouths of rivers, v. v. 
10. Mactra minutissima. Minute Mactra . 
Montagu, Suppl. p. 37. 
Shell white, nearly smooth, somewhat triangular, smooth 
within with a plain margin: beaks prominent, strong ; 
i binge with two primary teeth in one valve, separated by a 
carity for the reception of a single tooth in the other. 
Except for its triangular outline this species has a close 
alliance to the genus Tellina. It (lifters from M. triangu¬ 
laris, in its size, which is little more than a line long and 
two broad, in the teeth, and in the want of the notched 
margin. 
Devon coast, and Dublin bay. v. v. 
11. Mactra 
