or 



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 ivith the ligament marginal, partly included, linear, extending along 

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

 byssus. 



GENUS Mf TILUS, 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 with a few denticulations ; epidermis dark-bluish, shell 

 violet beneath. 



FIGURE 82. 

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



My'tilus edulis, LIN.; Syst. Nat., 1157. GMELIN ; Syst., 3353. TURTON; LIN. j 



iv. 291. CHEMN. ; Conch., viii. 169, t. 84, f. 750. PENNANT j Brit. Zool, iv. 



236, t. 66, 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. Meth., Vers, ii. 562, pi. 218, f. 2. KNORR; Vergn., iv. pi. 



15, f. 4. LAM. ; An. 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, 1. 15, f. 5. 

 Musculus subcseruleus ; 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 



