LEA ON THE GENUS ACOST^A OF D'ORBIGNY. 129 



a son tour, etre une Huttre." He expresses the opinion that this specimen came from 

 the same country as Etheria, Madagascar or Africa, but it is much more likely, that 

 this noted specimen got into the collection, separately from those of Etheria — that it 

 really came from South America, and the difference not being observed, was mixed 

 with the Etheria. 



M. Ferussac, considering the general resemblance of Mulleria to Ostrea, thought 

 that it ought to be put along side of, if not in, the genus Ostrea, but Messrs. 

 Brongniart and Latreille did not in their report agree with him. They stated the 

 importance of the characters drawn from the muscular impressions, and after examining 

 the assimilating genera, came to the conclusion with Cuvier that the genus Etheria 

 ought to be associated with the ChamacecB, shells alike inequivalve and affixed to 

 various substances, while they considered that Mulleria properly belonged to a small 

 natural Family, well characterized by the form and situation of the ligament, and 

 which Cuvier placed between Spondylea and Arcacea. They expressed the opinion 

 that Mulleria was more likely to be estuary than fiuviatile, properly so called. But 

 M. d'Orbigny's Acostcea being found so far in the interior of New Granada, does not 

 sustain this idea, but determines it like Etheria, to be an inhabitant of fresh water, 

 far removed from the sea. 



M. Ferussac's opinion seems to have been carefully considered. As regards 

 Etheria, he says, that the genera Chama, Etheria and Ostrea, are all equivalve, and 

 fix themselves on some body, and are deprived of locomotion. But he thinks it 

 necessary to know the animal, to be able to place it properly, whether in Chamacea or 

 Ostracea, two families very distinct. 



As regards Mulleria, he says that the hinge and ligament present characters which 

 distinguish it from the true Ostrea. That it has an exterior ligament, short, lateral 

 and linear, perfectly similar to the Anodonta and Unio, and a little like to Perna 

 and Crenatula, as regarded a waved cardinal line. This line, he says, situated under 

 the beaks, is filled with ligamentous substance which binds the two valves together. 

 " Les Marteaux and les Femes sont byssifere; notre coquille {Mulleria) se fixe a la 

 maniere des Huitres et non par un byssus ; aussi son animal parait depourvu de pied." 

 The hinge being different from Perna and Malleus, and the inferior valve having a 

 long " talon," M. Ferussac comes to the conclusion that it must be put alongside of 

 or with the genus Ostrea. (p. 367.) 



Blainville in his Malacology places Etheria in the Family Chamacea, between Dicera 

 and Tridacna, but in the addenda to the volume he says, "it had better, perhaps, be 

 placed, as Sowerby thinks, among the Family Suhmytilacea. Mr. Sowerby's attention 

 has been given to the genus Etheria. He had observed that it had two muscular 

 impressions, which induced him to conclude that it belonged to fresh water or to 

 estuaries. Sowerby's attention was also drawn particularly to the Mulleria, of which 



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