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 MYTILACEA, Lam. 



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

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

 byssus. 



Genus MYTILUS, Lm. 



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 xvith a few denticulalions ; epidermis dark-bluish, shell 

 violet beneath. 



Figure 82. 



State Coll., No. 15G. Soc. Cab., No. 1987. 



My'tilus edulis, LiN.; Syst. Nat.,\\^7. Gmelin ; St/sL, 3353. Turton; Lin.; 



iv. 29L Chemn. ; Conch., viii. 1G9, t. 84, f. 750. Pennant ; Brit. Zool., iv. 



236, t. 66, f. 2. Montagu ; Test. Brit., 159. Lin. Trans., vi. t. 18, f^ 13, 14. 



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



Deshayes; Encyc. M6th., Vers, ii. 562, pi. 218, f. 2. Knorr; Vergn., iv. pi. 



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



Brit. Shells, t. 128. Wood ; Index, pi. 12, f. 21. Fleming ; Brit. Anim., 411. 

 My'tilus vulgaris. Da Costa ; Brit. Conch., 216, t. 15, f. 5. 

 Musculus subcaeruleus ; Lister ; Conch., t. 362, f. 200. 

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



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

 placed at one 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 



