MACTRA, 
S5 
the front margin thin and plain, the nipper edges on each 
side the hinge thick and flattened, and gradually curving on 
both sides : hinge with a spoon-shaped cavity in one valve, 
and a thin oblique tooth each side; in the other a similar 
cavity, with a triangular tooth on one side, and a thin obr 
lique one on the other, without lateral ones : in young 
shells are two prominent sharp transverse teeth in one 
. valve, receiving the triangular tooth of the other between 
them: length two inches and a half: breadth four and a 
half. 
Variety. Of a more oblong shape, being three times as 
wide as it is long, with the margins forming nearly a 
straight line, and about half the size. The specimen under 
our examination was dredged up at Cove, near Cork, and 
in the teeth and general appearance exactly resembles a 
more produced variety of this species. 
At the mouths of rivers, v. v. 
14. Mactra hyans. Oblong Mactra. Fig. 41. 
Da Costa , pi. 17- f. 4— Donovan , pi. 140 — Dorset Cat. 
pi. 2. f. 4 —Linn. Trans, vi. pi. 16. f. 5, 6. 
Shell oblong-oval, thick, strong, nearly opake, rounded 
arid somewhat gaping at the larger end; the anterior side 
elongated, a little contracting and curving in a somewhat 
scymctar-shaped form, the end considerably gaping, with a 
slight'angular tendency : color dull white, with a reddish 
yellow tinge towards the hinge: beaks near one end, 
pointed and incurved, from winch there is a considerable 
slope or indenture towards the smaller end, and a strong 
groove which runs along the margin on the outside ; from 
the beaks is also a depressed line on the outside extending 
to the lower end of the front margin ; inside dull white, 
with a ferruginous patch under the hinge on the broader 
side, the margin plain and thin: hinge with a spoon-shaped 
cavity and two plain laminar teeth behind it in one valve ; 
in the other two teeth behind the cavity, one of wliich is 
thick and cloven, the other thin and plain; lateral teeth, 
none: length, of the specimen before us, two inches and 
three quarters; breadth five inches and a half. 
This elegant shell is readily distinguished from M. Lu- 
traria, by its elongated and rather scymetar-shaped form; 
i by 
