114 
MYTILUS. MUSSEL, 
those large detached masses which are scattered under 
the cliff at Torquay, near the entrance to the strand from 
the Tor-abbey fields. The Mytilus lithophagys, indepen¬ 
dently of the transverse strife which cross the concentric 
ones on the cartilage side, is very convex and rounded on 
the bach, giving the shell a somewhat cylindrical appear¬ 
ance when the valves are closed ; the beaks are also ter¬ 
minal and somewhat pointed, like those of the M. Modio¬ 
lus, with the opposite extremity rounded. Mr. Dillwyn 
has referred Lister’s figure (which is an excellent one, and 
marked as English,) to the Solen minutus, which is trun¬ 
cate at the hinge end. Those which we have collected 
from among the roots of Fuci and Sertularife, are much 
more irregular in their figure, but all sufficiently retaining 
their specific marks, v. v. 
13. Mytilus plicatus. Plaited Mussel. 
Chemn. Conch. viii. pi. 82. f. 733. a, b. 
Shell oblong, very thin, transparent, dirty white, uneven 
on the surface, slightly plaited and irregularly wrinkled 
transversely, rounded on the side next the hinge, anguinr 
and dilated on the other, causing it to be a little larger, 
where it gapes ; inside glossy, rather perlaceous: hiiWe 
near the rounded and smaller end ; beaks small, a little in¬ 
curved : length not half an inch; breadth double its length 
Isle of Sky, and Dublin bay: rare. v. m. 
14. Mytilus decussatus. Decussated Mussel. 
Chemn. Conch, viii. pi. 85. f. 761. 
Shell longitudinally oval, thin, transparent, very convex, 
covered with a pale olive skin, under which it is pearly 
white, finely striate longitudinally, and crossed by more 
minute transverse lines ; inside smooth, perlaceous • the 
sides equal ; beaks close to the smaller end, with a slight 
indenture, and the contiguous margin is faintly denticu¬ 
late ; and near the front margin is a singular reflected trans¬ 
verse ridge : length the eighth of an inch ; breadth not so 
much. 
Only one valve of this shell was found by Captain Las¬ 
key, on the Scotch coast: its convexity gave it the appear¬ 
ance of a Patella; but the hinge is that of a bivalve desti¬ 
tute of teeth. 
