MYTILUS. 289 



Four genera pertain to the Mytilacea — Lithodomus, 

 Mod'wla, Mijtilus, and Pinna. 



The first two genera are both peculiar in their habits. 

 The first dwells in concealed cavities, among stones and 

 madrepores, where he excavates a dwelling, and has conse- 

 quently no occasion for a byssus or anchor ; the second 

 resembles the My till in his habits, and his shell differs only 

 in the short obtuse termination of the anterior side. 



Mytili are strictly marine, and yet one or two species, 

 which have affixed themselves to vessels, and been carried in 

 consequence into canals or docks, have become localized in 

 fresh water. 



Several species are included in the genus, and in these 

 what great variety ! Some are smooth, beautifully marbled, 

 and variegated with delicate colours ; others are elegantly 

 radiated with white and purple ; others, again, consist of 

 only one colour, being either black or blue, green, or 

 brown, or yellow, coarsely ribbed, and grained with minute 

 tubercles. Some exliibit internally a pearly appearance; 

 others, when uncoated from a shaggy epidermis, display 

 considerable brilliancy. 



A recent traveller relates that a silvery kind of Mussel, 

 much in request among the Indians of North America, 



