FAMILY 13. CHAMACEA. 125 



cular points of attachment are rather indistinct, being but faintly im- 

 pressed ; the anterior one is compound. 



Example. 



PL XCIV. Fig. 1 and 2. 



Mycetopus soleniformis, D'Orbigny, Magazin de Zoologie, 1835, p. 41 . 



Voyage dans l'Amerique Meridionale, Mollusques, pi. 66. f. I to 3. 

 Mycetopus solenoides? Sowerby, Jun., Conch. Manual. 



Family 13. CHAMACEA. 



Testa inrequivalvis, irregularis, affixa ; cardine dente unico crasso, inter- 

 dum obsoleto. Animal aut fluviatile aut marinum. 



The important distinction as to whether the Tropiopodous mollusk 

 is attached to its shell by one or two muscles, appears to have escaped 

 the notice of Linnaeus ; it is not, therefore, a matter of surprise that he 

 should have associated in his genus Chama both unimuscular and bimus- 

 cular species. Few of these are included in Lamarck's family of the 

 Cliamacea ; some, as we have already shown (vide p. 101), are referred 

 to the family of the Cardiacea, others to that of the Tridacnacea (Order II. 

 Unimusculosa). There is, however, one of the two genera into which the 

 Chamacea are divided, which we have not retained without considerable 

 reluctance ; in fact, it is only from a fear of being guilty of innovation 

 that we have refrained from associating the Etheriee in a new and sepa- 

 rate family, or, rather, from regarding as families the divisions that are 

 here determined as genera. There is evidently a wide and unnatural gap 

 in this part of the system ; and we think it not improbable that new forms 

 and varieties may yet be discovered, to reduce the apparent want of 

 affinity between the Etheriee and the Chama. 



The shell of the Chamacea is characterized as being irregular, inequi- 

 valve, and always attached by one valve to some other body. The hinge 



