46 CLASS I. TROPIOPODA. ORDER I. BIMUSCULOSA. 



GLYCIMERIS, Lamarck. 



Testa aequivalvis, crassa, transversa, utroque latere latissime hians ; 

 epidermide nigra induta, valvarum marginem superante. Cardo 

 callosus, edentulus, liganiento magno, externo. Impressiones mus- 

 culares distantes ; impressio pallii profunde imbuta. 



The genus Glycimeris was instituted by Lamarck ; it had been previ- 

 ously associated with the Mya, but upon detecting the affinity of its 

 characters with those of some of the Solenacea, he referred it to this 

 family ; and the propriety of the removal has been since confirmed by 

 the anatomical demonstration of the animal by M. Ardouin. 



The shell of Glycimeris is equivalve, thick, transverse, gaping widely 

 at both ends, and covered with a thick, black, horny epidermis passing 

 over the edge of each valve. The hinge is entirely destitute of teeth, 

 and the interior of the shell is remarkable for the strong impression of 

 the mantle. The ligament, as in all the Solenacea, is external ; but in 

 this genus the position of it is reversed, being placed on the short side of 

 the shell above the umbones, which are generally much eroded. 



Example. 



PI. XXVIII. Fig. 1 and 2. 



Glycimeris siliqua, Lamarck, Anim. sans vert., new edit., vol. v. 



p. 69. 

 My a siliqua, Chemnitz. 

 Mya picea, Wood. 



SOLEMYA, Lamarck. 



Testa sequivalvis, inrequilateralis, transversim oblonga, ad extremitates 

 obtusa ; epidermide nitida induta, marginem superante ; umbonibus 



