FAMILY 2. MYTILACEA. 139 



PI. CI. Fig. 5. 



Modiola tulipa, Lamarck, Anim. sans vert., vol. vii. p. 18. Enc. 

 Meth., pi. 221. f. 1. 



Mytilus modiolus ? Linnasus. 



PI. CI. Fig. 6. 



Modiola semifusca, Lamarck, Anim. sans vert., vol. vii. p. 22. Sow- 



erby, Genera of Shells, No. 26. 

 Mytilus semifuscus (Deshayes ?) . 



PI. CI. Fig. 7. 



Modiola plicatula, Lamarck, Anim. sans vert., vol. vii. p. 22. Enc. 



Meth., pi. 220. f. 5. a, b. 

 Mytilus plicatulus, Deshayes. 

 Mytilus dernissus, Dillwyn. 



MYTILUS, Linnaeus. 



Testa aequivalvis, obliqua, subtrigona vel cuneiformis ; umbonibus acutis, 

 subrectis, terminalibus ; latere postico rotundato. Cardo edentulus, 

 raro subcrenulatus, ligamento marginali, subinterno. Impressio mus- 

 cularis composita, sublateralis. 



The Mytili, as we have already shown, are so intimately allied to the 

 Modiola, that many authors have thought it expedient to unite them. 

 The former may, however, be recognized by the depressed and longitu- 

 dinally-triangular form of their shell ; whilst, in the latter, the shell is 

 convex, and obtusely terminated on the anterior side. The Mytili are 

 strictly marine ; but one or two species, which have been carried into 

 canals or docks through getting fixed to the bottoms of vessels, have 

 become localized to fresh water. One of these, the Mytilus polymorphus, 

 originally found by Pallas in the river Wolga, and described by him in 



t2 



