MYOCHAMA. 



TESTA inaequivalvis, irregularis, adhaerens ; 

 valva affix^ deiitibus duobus marginalibus, di- 

 varicatis, ad umbonem disjunctis, foveola 

 trigona intermedia alteram testacese appendicis 

 extremitatem, jcartilagine cornea connexam, 

 excipiente; valva libera dentibus duobus iii- 

 sequalibus, parvis, divarieatis, altera appendicis 

 .extremitate foveolse intermedias inserta. Um- 

 bones valvae liberae intern^, alterius extern^, 

 recur vi. Impressiones muscular es duae, orbicu- 

 lares, distantes, laterales. Impressio pallii 

 sinu brevi, lato. Ligamentum tenue, externum. 



A NEW and very singular Genus of bivalve shells, lately 

 discovered and first described by Mr. S. Stutchbury in the 

 5th vol. of the Zoological Journal, p. 96, It was found 

 attached to a smooth species of Pcctunculus and to Tri- 

 gonia pectinata at Port Jackson, New South Wales; and 

 it has been named Myochama from the circumstance of its 

 connecting in itself some of the characters of the Myarice 

 and ChamacecB, In general appearance Myochama bears 

 so near a resemblance to Anomia, that if particular atten- 

 tion be not paid to its internal characters and the mode of 

 its adherence, it might be easily mistaken for that Genus. 

 The two distant lateral muscular impressions, and the 

 absence of the shelly appendage by which Anomia is 

 attached, easily distinguish it. We have said that Myo- 

 chama combines in itself some of the characters of the 

 MyaricB and the Chamacece ; those which it has in common 

 with the ChamacecB are its muscular impressions, and its 

 being attached by the outside of one valve ; while it has in 

 common with some of the Myarics an internal shelly ap- 

 pendage in the hinge : from Lamarck's Genus Anatina it is 

 distinguished by its being an irregular and adherent shell. 



