MYTILACEA. MOLLUSCA. MYTILUS. 121 



and the size of adults is seldom more than two thirds of the dimen- 

 sions above given. It is one of the connecting links between Alas- 

 MODON and Anodon, 



Family MYTILAcEJI, Lam. 



Hinge with the ligament marginal, partly included, linear, extending along 

 a great part of the posteiior border. Shell rarely foliated ; adheres by a 

 byssus. 



Genus MYTILUS, Lin. 



Shell elongated.) sub-triangular ; beaks terminal, pointed, 

 straight ; hinge generally toothless ; muscular impression elongated, 

 club-shaped. 



My'tilus edulis. 

 Shell ovate-triangular, beaks terminal and pointed, basal margin 

 straight, ligament margin straight ; posteriorly widened and round- 

 ed ; hinge ivith a few denticulations ; epidermis dark-bluish, shell 

 violet beneath. 



Figure 82. 

 State Coll., No. 156. Soc. Cab., No. 1987. 



My'tilus edulis, LiN.; Syst. JVat., IUj7. Gmelin ; S(/s/., 335.3. Tdrton; Lin.; 



iv. 20L Chemn. ; Conch., viii. 1G9, t. 84, f. 750. Pennant; Brit. Zool., iv. 



23G, t. G6, f. 2. Montagu ; Test. Brit., 159. Lin. Trans., vi. t. 18, f. 13, 14. 



DiLLWYN ; Catal., 309. Turton ; Conch. Diet., 109. Brit. Biv., 196. 



Deshayes ; Encyc. Mith., Vers, ii. 5G2, pi. 218, f. 2. Knorr; Ffr^n., iv. pi. 



15, f. 4. Lam. ; An. sans Vert., vii. 47. Gualt. ; Test., t. 91 , f. E. Donovan ; 



Brit. Shells, 1.128. Wood; Index, p\. 12, f. 21. Fleming ; Brii. .^«m., 411. 

 My'tilus vulgaris, Da Costa ; Brit. Conch., 216, I. 15, f. 5. 

 Musculus subcceruleus ; Lister ; Cunch., 1. 362, f. 200. 

 My'tilus borealis, Lam.; An. sans Vert., vii. 46. 



Shell triangular-ovate, solid, coarse, shining ; beaks pointed, 

 placed atone end, and slightly diverging ; basal or anterior margin 

 generally straight, sometimes slightly convex, and sometimes ex- 

 cavated ; hinge margin rising in a straight line unites with the 

 upper or posterior margin by a somewhat abrupt curve ; this mar- 

 gin takes a direction parallel to the base, for a short distance, and 

 then the two unite by a regular curve ; an abrupt ridge passes 

 from the beaks to the lower and hinder angle, above which the 

 shell gradually slopes to a sharp edge, and below which it bends 

 so abruptly as to present a broad, flattened space, in the centre of 



16 



