84 CONCHIFERA. MONOMYAIRA. 



' The shells of this genus are marine, the greater part large, and thin in proportion 

 to their size. They are of a longitudinal form, narrowed into a point at their base, 

 widened and rounded upwards. The animal is elongated, without projecting syphons, 

 and has a conical foot, which serves to fix the byssus. The byssus of this genus, 

 however, in place of being thick and coarse like that of the Mytili, is long, fine, 

 shining, silky, and very abundant. Of this byssus gloves and other articles are 

 sometimes made. The Pinna is said to have been so called from its resemblance to 

 the plumes which the ancient Romans wore on their helmets. 



P. rudis, Lin. Shell oblong, with six or eight longitudinal round- 

 ed ribs, armed with membranaceous vaulted scales ; colour dark 

 red, or liver-colour. 8 inches long. Inhabits the American Ocean. 

 Lister, pi. 373, fig. 214. 



P. nobilis, Lin. Shell subtriangular-oblong, with twenty-four lon- 

 gitudinal spinous ribs ; spines somewhat tubular ; colour pale 

 reddish. Atlantic and American seas. Bonan. 2, fig. 24. 



P. muricata, Lin. Shell subtriangular, horn-coloured and pellucid, 

 with about sixteen or eighteen longitudinal ribs, which are al- 

 ternately broader and spinous. 5| inches long. Inhabits Ame- 

 rican seas Lister, pi. 370, fig. 210. 



P. ingens, Maton. Shell subtriangular-ovate, slightly incurved to- 

 wards the summit, with irregular scaly wrinkles, and interrupted 

 longitudinal striae. 1 foot long. Inhabits coasts of Britain. B. 

 Browns Illust. pi. 30, fig. 1. 



Gen. 28. MYTILUS, Lin. Lam. 



Shell longitudinal, equivalve, regular, pointed at the base, and 

 adhering by a byssus ; beaks almost straight, terminal, and 

 pointed ; hinge lateral, generally without teeth ; ligament 

 marginal, subinterior; muscular impression elongated, clavate, 

 sublateral. 



The shells of this genus are all marine, and many are found fossil. 



* Shell furrowed longitudinally. 



M. Magellanicus, Lam. Shell oblong, angular, and white below, 

 above purplish violet ; longitudinal furrows thick, \vaved ; beaks 

 acute. 5 inches long. Inhabits American seas. Lister, pi. 356, 

 fig. 193. 



M. exustus, Lin. Shell oblong, longitudinally striated ; belly angu- 

 lated, tumid ; margin crenulated. 2 inches long. Inhabits 

 American seas. Lister, pi. 365, fig. 205. 



M. Senegalensis, Lam. Shell small, narrow, depressed behind, 

 longitudinally sulcated ; beaks curved, divaricate ; colour white 

 at its base and posterior side, the rest purple, f inch long. In- 

 habits African seas. Lam. vi. 1, 122. 



** No longitudinal furrows. 



M. elongatus, Lam. Shell elongated, narrow, straight, white pos- 

 teriorly, the rest violet ; sides depressed behind ; base bidentate. 

 5^ inches long. S. American seas Favanne, pi. 50, fig. 1. 



M. smaragdinus, Lam. Shell subtrigonal and compressed ; epi^ 



