THE PEARL OYSTER. 949 



Cuvier, in his " Regne Animal," places in close con- 

 tact with Avicula and the pearl-oysters the genus Etheria 

 of Lamarck, and which writers regard as belonging to the 

 Chamidse. Blainville, Deshayes, and Broderip, however, 

 all agree that the Etheriae ought to be separated from the 

 Chamidae ; and Blainville considers them as coming within 

 the pale of the Margaritacea, or family of pearl-oysters. 



Lamarck regarded the Etheriae as oceanic, and accounted 

 for those shells having escaped the notice of zoologists on 

 the presumption that they were attached to rocks at great 

 depths. The first conchologist who ventured to doubt 

 this, and to suspect them to be fluviatile, or at least the 

 inhabitants of estuaries at the mouths of rivers, was 

 Sowerby ; his opinion was confirmed by Cailliaud, who 

 was the first to make known the fact that the genus is an 

 inhabitant of fresh waters. From Cailliaud's materials 

 Fe"russac published a paper in the " Memoires de la 

 Soci6te d'Histoire Naturelle," vol. i, including a revision 

 of the species. 



Rang, during a voyage to Senegal, made some inter- 

 esting observations on the Etheriae, wbich live 200 leagues 

 from the mouth of the river of Senegal, and, together with 

 Cailliaud, who received the animal from the Nile, pub- 

 lished a memoir (" Memoires du Museum d'Hist. Nat."), 

 replete with information, in which the mollusc was for the 

 first time described. 



The rivers of Africa and Madagascar appear to have 

 afforded all the specimens, still by no means common in 

 cabinets, which have hitherto been collected. M. Ferussac 

 gives the following information from M. Cailliaud :- 



" We meet with Etheriae," says that zealous traveller, 

 " after passing the first cataract, and they do not appear to 

 exist below ; they become very abundant in the province 



