62 MYTILID^E. 



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 branchiae, 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 branchiae, 

 smooth within and strongly striated externally. 



This very elegant species is frequently taken alive in the 

 coralline zone at Exmouth. It differs very materially in the 

 organs from its congener M. barbata. 



M. MODIOLUS, Linnaeus. 



M. modiolus, Brit. Moll. ii. p. 182, pi. 44. f. 1, 2. 

 M. phaseolina, Brit. Moll. ii. p. 186, pi. 44. f. 3, juv. 

 M. Ballii, Brown. 



-, Brit. Moll. ii. 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. Ballii 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, pi. 45. f. 4. 



Animal suboval, thick, pale yellow ; mantle closed on the 

 anterior ventral half, at which point 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 branchiae. The 

 foot is white, with a deep byssal groove, from which a strong 



