NORTH BRITISH TESTACE A. 3§I 



a few species ; with generally a subulate exca- 

 vated longitudinal line. 



Mytilus. 



1. edulis. P. D. M. On all parts of the coast P 



common. 



% incurvatusr. P» M. Montagu wishes this spe- 

 cies to be reckoned a va- 

 riety of edulis, but I can- 

 not accede to his opinion: 

 the formation of the 

 valves is distinct, and does 

 not vary : their habitat 

 is also totally distinct. 

 This species is generally 

 found single among the 

 gravel, or in holes in 

 rocks, while edulis is 

 found in beds of large 

 size ; and it may appear 

 strange, that I never dis- 

 covered incurvatus among 

 the immense beds of mus- 

 cles at Musselburgh, tho* 

 among the rocks at Dun- 

 bar they are, though not 

 common, to be found ; most 

 of the specimens taken 

 there have a small indent 

 on their frontal margin, 

 ■which seems also to be 

 characteristic of this spe» 

 cies. 



Bb 4 



