316 MYTILUS. 



thin, fragile, semi-pellucid, transversely wrinkled, aud co- 

 vered with an olive or yellowish green epidermis; it differs 

 from M. anatinus in being larger and more convex, and in 

 not being equally compressed at the margin on both sides of 

 the hinge. Muller however has justly observed that it is often 

 very difficult to distinguish these species, and his M. radiatus 

 appears to be an intermediate variety ; the inside is white and 

 pearly. Gmelin says that his M. Zellensis is allied to M. 

 Cygneus, but Schroeter, from whose figure in the Flusscon- 

 chylien it is taken, considered it to be the Linnaen Mya are- 

 naria, and it is too doubtful a species to be retained. The 

 animals of the fresh water muscles are similar to those of 

 Mya pictorum and its congeners, and are not furnished with 

 a Byssus. 



fluviatilis. 34. Shell transversely oval, rounded 

 on both sides and smooth ; umbones large, 

 rounded, and the summits inflected. 



Mytilus fluviatilis. Gmelin, p. 3359- 



Mytilus ilhtus, Sotanders MSS. Portland Cat. p. 163. 

 lot 35 51, 



Mytilus, No. 22. Schroeter Einl. iii. p. 459. 



Lister Conch, t. 157. f. 12. 

 Inhabits the rivers of North America. Solander. Virginia, 



Lister. 

 Shell about two inches long, and rather more than three broad ; 



and Lister says that the inside is reddish. 



stagnalis. 35. Shell transversely oval, flattish, 

 and somewhat ribbed transversely. 



Mytilus stagnalis. Gmelin, p. 3362. Sowerby Brit. Misc. 



t. 16. ? Montagu Supp. p. 68. ? 

 Mytilus, No. 49- Schroeter Einl.m. p. 467. 

 Musculus maximus planior viridens edentulus. Schroeter 

 Flussconch. p. 159- t. 1. f. 1. 



Inhabits the Lake of Schwansee. Schroeter. 



Shell five inches and a half long, and eight inches and three 

 quarters broad ; of a greenish colour, becoming yellowish 

 brown towards the margin, and marked with darker longitu- 

 dinal rays ; it is said to be flatter and narrower in proportion 

 than M. Cygneus ; the shell found by Mr. Sowerby in Kew 

 Gardens is on the contrary said to be more convex than M. 

 Cygneus, and is probably only a variety of that species. 



