128 CLASS I. TROPIOPODA. ORDER I. BIMUSCULOSA. 



vers, vol. ii. p. 121. De Blainville, Manuel de Malacologie, 



p. 543. 

 Var. Etheriaplumbea, De Ferussac. 

 Var. (spinosa) Etheria Carteroni, Michelin. 



CHAM A, Linnaeus. 



Testa irregularis, plerumque suborbicularis, injequivalvis, adhaerens ; 

 umbonibus intequalibus, distantibus, involutis. Cardo dente unico 

 crasso, obliquo, subcrenato, in fossula valvar oppositae inserto. Li- 

 gamentum externum, divaricatura, sub umbonibus revolutum. 



Bruguiere was the first to reform the Linnsean genus Chama, and it is 

 now reserved only for those well-known parasitical species so frequently 

 found adhering to the shells of other mollusks. The Chamae have for 

 the most part a delicately coloured shell, ornamented with numerous 

 spines or foliations ; but it is often much distorted, according to the 

 situation in which it is confined. They become attached either by the 

 upper or lower valve, and grow very irregularly, with the umbones 

 turned either to the right or to the left. 



Tbe shell of Chama may be described as being irregular, generally 

 suborbicular, inequivalve, and is always found adhering to some marine 

 body ; the umbones are unequal, distant, and turned inwards either to 

 the right or to the left. The hinge consists of a single thick oblique 

 tooth, which is a little crenated, and inserted in a small pit in the oppo- 

 site valve. The ligament is external, divaricate, and rolled back under 

 the umbones. 



Examples. 



PI. XCVI. Fig. 1. 



Chama Dam^ecornis, Lamarck, Anim. sans vert., new edit., vol. vi. 

 p. 580. Enc. Me'th., pi. 197. f. 1, a, b, c. 



