262 MYTILID-S!. 



The common edible mussel frequents mud-banks which are 

 uncovered at low-water ; the fry abound in water a few fathoms 

 deep ; they are full-grown in a single year. From some imknown 

 cause they are at times extremely deleterious. The consumption 

 of mussels in Edinburgh and Leith is estimated at 400 bushels 

 (= 400,000 mussels) annually ; enormous quantities are also 

 used for bait, especially in the deep-sea fishery, for which pur- 

 pose thirty or forty millions are collected yearly in the Frith of 

 Forth alone. — Dr. Knapp. Mussels produce small and inferior 

 pearls. At Fort Stanley. Falkland Islands, Mr. Macgillivray 

 noticed beds of mussels which were chiefly dead, being frozen at 

 low-water. 



The species of Mytilus are usually found attached by a byssus 

 in masses to stones, wrecks or floating bodies. The ligulate 

 grooved foot has the power of spinning the silky material of the 

 byssus whenever the animal requires temporarily to anchor itself. 



Boughs of elm and other trees are laid down in the Bay of 

 Kiel, and taken up at the end of three, four, or five years, between 

 December and March, being then covered with fine mussels. 

 These laden boughs are sold by weight, and the shell harvest is 

 sent into the interior of Germany, where it is in great request. 



AULACOMYA,Morch. (Hormomya,Morch. Arcomj'tilus, Agass.) 

 Surface ornamented with radiating ribs. M. decussatus, Lam. 

 (cxxviii, 92). 



CALOROMYA, Morch. M. afer, Gmel. (cxxviii, 93). 



MYTiLOCONCHA, Cour., 1862. Subfalcate, thick, perlaceous, 

 laminated ; hinge thick, elongated ; pointed at the apex ; an 

 oblique tooth or ridge and parallel furrow throughout the entire 

 length of hinge-area. M. incurva, Conr. (cxxii, 11). 



BYSSOPTERIA, Hall, 1883. Shell erect, alate posteriorly, trun- 

 cate with a nasute projection in front ; surface radiated. M. 

 radiata, Hall. Fossil ; Chemung Group, N. Y. 



MYTiLOPS, Hall, 1883. Shell resembling Modiola and Litho- 

 domus in external form, and may also be compared with the 

 fossil genus M^^oconcha ; hinge-line narrow, oblique, extending 

 about one-half the length of the shell ; beaks terminal. 4 sp. 

 Chemung Group, New York. M. preecedens, Hall. 



STAVELiA, Gray, 1857. Shell inequivalve, inferior margin sinu- 

 ous. M. torta, Dunker. 



MoDioLA, Lam., 1199. 



Etym. — Modiolus^ a small measure, or drinking-vessel. Horse- 

 mussel. 



Syn. — Perna, Adanson, H. and A. Adams. Araygdalum, 

 Muhlf. Callitriche, Poll. 



Distr. — 70 sp. Universal. Chiefly tropical. M. modiolus. 

 Arctic seas — Britain. Fossil, 150 sp. Silurian? Lias — ; United 



