I 
82 MACTRA, 
transverse furrows, yellowish-white: te&a pern- 
¥*\; the sides equal, much flattened and 
truncate, and the front margin rounded: beaks verypromi- 
nent and strong, quite central; teeth as in the last: length 
an inch and a half; breadth a little more. 
It is difficult to appropriate accurately the figures to this 
species and the last: so difficult that Mr. Dillwyn has re* 
ferred to Da Costa’s figure of M, solida for M. truncata, 
and to the copy of the same figure in the Dorset Catalogue 
for Mi solida. ♦ 
Northern and western coasts, and Dublin bay, v. v. 
/. Mactra subtruncata. Oval Mactra. 
Pennant , pi. 55. f. 1— Montagu, pi. 27. f. 1—Linn. Tram, 
viii. pi. 1. f. II —Dorset Cat. pi. 5, f. 10— Lister, pi. 252. 
f. 86? 
Shell convex, thin, semitransparent, yellowish horn-color 
covered with a pale brown skin, rather glossy, very rough 
and brown at the anterior side, a little truncate both sides, 
one of which is rounded, the other elongated and rather 
angular at the end, the edges of both of them prominent 
and much turned inwards, particularly on the shorter side 
where a heart-shaped depression is formed, faintly but re- 
gularly striate transversely, and more strongly so towards 
the rounded end : beaks not central, pointed and very pro. 
minent; inside glossy, white or with a yellowish cast^ la¬ 
teral teeth large and prominent, double in one valve, the 
double ones strongly striate internally only, the single ones 
striate on both sides: length three quarters of an inch; 
breadth an inch. 
Variety. Stronger, opake, more convex, of a more trian¬ 
gular shape, and not so much produced at one end, regu¬ 
larly and strongly striate transversely. 
Western coasts, Dublin bay, and North Britain, c. r. 
8. Mactra triangularis. Triangular Mactra. 
Montagu, pi. 3. f. 5. 
Shell strong, smooth, somewhat triangular, a little pro¬ 
duced on one side, opake, white; within white, but not 
much glossed, and strongly’ notched at the margin: beaks 
prominent; the primary tooth in one valve large and cloven; 
ip the other valve two small teeth, with a triangular cavity 
between 
