PBENA. CONCHIFERA. 83 



M. vulgariSy Lam. Shell trilobed, black, flexuose, distorted. 5 or 

 6 inches long. Inhabits Indian seas. D'Argenv. pi. 19, fig. A. 



M. anatinus, Lam. Shell elongated, slightly beaked on one side 

 towards the hinge, and much incurved on the other ; colour white, 

 tinged with violet, and pellucid. 3 inches long. Inhabits In- 

 dian seas. Chem. viii. pi. 20, fig. 658. 



Gen. Q5. PEKNA, Lam. Ostrea, Lin. 



Shell subequivalve, flattened, slightly distorted, and of a lamel- 

 lar texture ; hinge linear, marginal, composed of sulciform, 

 transverse, and parallel teeth, not alternating, between which 

 the ligament is inserted ; a sinus under the extremity of the 

 hinge for the passage of the byssus. 



P. ephippium, Lam. Shell suborbicular, compressed, much produc- 

 ed and rounded on one side ; margin acute ; colour purplish black 

 or ferruginous j inside pearly. 2 to 5 inches long. Inhabits In- 

 dian seas. Klein, Ost. pi. 8, fig. 18. 



P. isogjiomum, Lam. Shell compressed, elongated above into a 

 curved or oblique wing ; base transverse, produced into a beak 

 anteriorly ; hinge very long ; colour blackish violet ; inside pear- 

 ly. 5 to 7 inches long. Indian seas Humph. Mus. pi. 47, fig. 1. 



Gen. 26. CRENATULA, Lam. 

 Shell subequivalve, flattened, foliaceous, slightly irregular ; no 



particular opening for the byssus ; hinge lateral, linear, 



marginal, crenated ; the crenulations hollow to receive the 



ligament. 



The shells of this genus are in general thin, sometimes almost membranaceous, 

 fragile, and foliaceous. They are found in the seas of warm countries. 



C. amcularu, Lam. Shell rhomboidal, compressed, submembrana- 

 ceous, yellowish, rayed with white ; no sinus at the base. In- 

 habits South American seas. An. Mus. iii. pi. 2, fig. 1, 2. 



C. modiolaris, Lam. Shell wedge-shaped, compressed, submem- 

 branaceous, reddish, and rayed with white. Inhabits seas of 

 New Holland Lam. vi. 1, 137. 



FAMILY II. MYTILACEA. 



Hinge with the ligament subinterior, marginal, linear, very en- 

 tire, occupying a great part of the anterior border ; shell rare- 

 ly foliaceous. 



The greater part of the shells of this family attach themselves to marine bodies 

 by a byssus. They have a linguiform foot, by means of which they fix the filaments 

 of their byssus to extraneous bodies. 



Gen. 7. PINNA, Lin. 



Shell longitudinal, cuneiform, equivalve ; tumid at the summit, 

 pointed at the base, with the beaks straight ; hinge lateral, 

 and without teeth ; ligament marginal, linear, very long, al- 

 most interior. 



