MACH.ERA. 



47 



Macliara squcDua. 



three ; the first strong, ascending and curycd, the second still 

 stronger and widely branched, one branch being erect, the other 

 nearly prostrate, the third very much compressed, delicate, at right 

 angles with the first 

 and directed parallel 

 to the margin, just 

 under the ligament ; 

 on the other valve 

 two teeth, the first 

 ])rominent, a little 

 oblique, the other 

 very thin and ob- 

 liiiue, entering be- 

 tween the middle 



and last tooth of the opposite valve. Ligament quite protuberant. 

 Height, one inch and one fifth ; length, two inches and four fifths ; 

 width, three fifths of an inch. 



Not unfrequently taken from the stomachs of codfish caught at the 

 Banks, and sometimes off our shores. Bank Fisheries ( Stimpsoii). 



This species differs from all its co-species by the inclination of the 

 rib towards the longer side of the shell, and also by its apparent 

 u[»ward curvature. It is, however, very closely allied to the shells 

 figured l)y Wood and Conrad. 



It is very rare to find all the teeth entire. The two thin teeth 

 next the ligament are almost always broken ; but a careful examina- 

 tion will discover their vestiges ; and they never seem to be obsolete. 

 The erect tooth of the left valve is not unfrequently Ijroken, and per- 

 haps one of the branches of the bifurcated tooth. The large tooth 

 of the ridit valve is most constant. 



Machsera costata. 



Shell thin, smooth, shining ; epidermis greenish, zoned, and radiated with livid- 

 violaceous; internal rib inclining forward. 



Soten costatus, Say, Jom-n. Acad. Nat. Sc. ii. 315 (1822). — Valexc. in Chenn, 111. 



Conch, pi. 8, fig. 2. 

 Sokcurtus costatus, Say, Amcr. Conch, pi. 18.— Coxrad, Amor. yiav. Conch. 21, pi. 4, 



fig. 2. 

 Sukn Sai/ii, Griffiths Cuv. xii. pi. 31, fig 3. 

 Solen (Sulecurtoidcs) Nahantensis, Dks Moulixs, Actes de la Soc. Lin. do Bordeaux, v. 



109 (1832). 

 Machcera rosUita, Gould, Inv. 1st ed. 34 (1842). — Middexd. I\Ialac. Ross. ill. 78, t. 21, 



figs. 4-10. — De Kay, Nat. Hist. New York, 244, pi. 32, fig. 301. — Stimpson, 



Shells ofNew England, 22. 



