62 MYTILID A. 
filaments issues, by which the animal, wherever it may be 
placed, immediately attaches itself, and however frequently 
removed, refixes itself in a few minutes. On each side there 
are a pair of pale brown branchiz, narrow, linear, coarsely 
pectinated, but less on the inner than on the outer surface ; 
the palpi are short, pointed, triangular, and usually lie rolled 
together laterally ; they are of the same colour as the branchiz, 
smooth within and strongly striated externally. 
This very elegant species is frequently taken alive in the 
coralline zone at Exmouth. It differs very materially im the 
organs from its congener M. barbata. 
M. moptouvus, Linnzeus. 
M. modiolus, Brit. Moll. u. p. 182, pl. 44. f. 1, 2. 
M. phaseolina, Brit. Moll. ii. p. 186, pl. 44. f. 3, juv. 
M. Ballii, Brown. 
———., Brit. Moll. u. p. 192. 
The M. modiolus and its young shell, styled by some M. 
phaseolina, are seldom met with on the South Devon coasts. 
The M. Ballit is of very doubtful British parentage ; we can 
refer to no figure; and the animals of the first two have 
escaped our researches. 
CRENELLA, Brown. 
C. marmorata, Forbes. 
C. marmorata, Brit. Moll. ii. p. 198, pl. 45. f. 4. 
Animal suboval, thick, pale yellow; mantle closed on the 
anterior ventral half, at which poit is a large aperture for the 
foot ; the margin of the opening is plain, it is then closed, and 
forms a mixed purplish-red and flake-white membrane, which 
is produced into a small cylindrical anal tube, grooved at the 
base, with four or five minute dark cirrhi at the termination; 
and on its sides the mantle forms two pendulous puckered flaps 
of the same colour as the tube, with which the animal by bring- 
ing their margins into contact produces a canal, in conjunction 
with the groove, to convey the water to the branchiz. The 
foot is white, with a deep byssal groove, from which a strong 
