MYA. GAPER. 
99 
white and somewhat polished : hinge with a projecting 
hollow tooth in each valve, with a cavity on the cartilage 
side : length three-quarters of an inch ; breadth an inch 
and a quarter. 
Western coasts, and Dublin bay. v. v . 
4. Mva pubescens. Rough Gaper. Fig. 35. 
Mya deelivis. Wood , pi. 18. f.2 —Dorset Cat. pi. 4. f. 6. 
Shell oblong-oval, thin, semitransparent, yellowish- 
white, roughened all over like shagreen, rounded at one 
end, slightly truncate and angular, and a little gaping at 
the other, irregularly striate transversely; one valve deeper 
and larger than the other, so as in some measure to inclose 
it; the front margin often a little contracted near the mid¬ 
dle: beaks prominent, incurved, the points not placed quite 
opposite, but crossing each other, and forming an angular 
dope down the cartilage edge; inside white, but not glossy : 
hinge with a strong projecting hollow tooth in each valve, 
with a deep cavity on the posterior side, the opposite side 
projecting into a strong rib which runs along the middle 
of the cartilage edge forming a deep groove ; besides this 
is another rib which runs rather obliquely from the tooth 
towards the truncated end : length of the specimen before 
us two inches and a half; breadth three and a half; but it 
is seldom found so large. 
In the belief that these two shells are quite distinct, we 
are supported by the opinion of some highly respectable 
conchologisU. Although they arc sufficiently abundant 
on the Western coasts, no intermediate size has been yet 
discovered. One is roughened all over ; the other is quite 
smooth, except at the cartilage slope. The beaks of M. pur 
bcscens cross each other, like the mandibles of the Loxia 
curvirostra, or Cross-beak : but the most striking and ma¬ 
terial difference is the strong rib and groove along the car¬ 
tilage edge: there is also some difference in the teeth. 
For the present, therefore, we are inclined to offer them as 
distinct species, suggesting at the same time a close atten¬ 
tion to their natural history. 
In the Memoirs of the Wern. Soc. p 505. pi. 24. f. 4, Mr. 
Brown has described and figured a shell under the name 
pfM. pellucida, from the cabinet of Dr. Taylor of Dublin, 
k 2 which 
