MULLERIA, 



De Ferussac, 



TESTA irregularis, inaequivalvis, insequilatera- 

 lis, foliacea, ostreiformis, valva altera extern^ 

 fixa ; impressione jnusculari uniea, prope extre- 

 mitatem posticaiii (i. e. dorsalem) posita; em- 

 pr essione museulari pallii irregularl: ligamento 

 dorsali elongate, externo, in siniim posticum 

 deeurrente: umbonibus antieis, sublateralibus. 



One of the most singular and rare of known genera^ not 

 noticed by Lamarck, and only very recently remarked 

 by De Ferussac among the specimens of iEtheria, in 

 the Duke of Rivoli's collection. The two specimens that 

 exist in Paris, and the individual in my Brother's 

 collection, being all that are known at present. The 

 Genus is remarkable as being intermediate in its struc- 

 ture, between iEtheria and Ostrea, and as apparently 

 connecting the regular fresh water bivalves the 

 Naiads'* of Lam.) with the irregular marine bivalves, 

 {Ostrea, for example,) and with the genus -^Etheria, in- 

 asmuch as in the sinus at the posterior extremity of the 

 ligament it resembles the Naiads and the ^Etheria ; and 

 in its single muscular impression, as well as its general 

 form it approaches to Ostrea. 



The following are the characters of the Genus ; it is an 

 irregular, inequivalve bivalve, adhering by the outside 

 of one valve : the structure of the outside of the shell is 

 foliaceous, but the foliations are closely pressed, and do 

 not form any murications or other rugosity on the surface; 

 the inside has a thin pearly coat of a glaucous green colour, 

 and partly iridescent. It has only one muscular impres- 

 sion in each valve, which is placed near the back and 

 towards the posterior extremity, and from one corner of 



