AND OTHER FAMILIES. 199 



same opinion) to be the Mya margarififera of Linnaeus. It has all 

 the characters of this species, with the exception of the addition of the 

 thick lateral tooth, which our author does not describe, but could 

 scarcely have failed to have observed. Being possessed of this tooth, 

 it is of course a true Unio. Pfeiffer describes an old margaritifera 

 under the name of sinuata. He says " dente cardinali valido, subcon- 

 ico, laterali nullo." In the north of Europe, (for the sinuata exists 

 only in the south) he had not, perhaps, like ourselves, until recently, an 

 opportunity of examining the true sinuata of Lamarck. 



Unto elongata. This is the true Mya margaritifera of Linnaeus 

 and other authors. The Alasmodonta arcuata of Barnes is its ana- 

 logue in this country. It inhabits the north of Europe, lake Ladoga, 

 Norwa}^, &c. 



Unio crassidens. The specimen quoted from Lamarck's own col- 

 lection, which is now in the possession of the Duke de Rivoli, is the 

 cuneatus of Barnes. Var, a is the trapezoides (nobis), a shell very 

 different in its general characters, being always folded. Crassidens 

 therefore has precedence of cuneatus. 



Unio Peruviana. This is the plicatus of Le Sueur, now so well 

 known in all our collections. Valenciennes says, Dombey's shell re- 

 mains in the museum, and that Lamarck described a North American 

 shell in error. The figure referred to by Lamarck, in the Ency. 

 Methodique, is certainly the well known plicatus of our western waters. 



Unio purpurala. Lamarck supposed the specimens he examined 

 to have come from Africa. I examined the specimen cited, in the 

 Duke de Rivoli's collection, as well, also, one in that of Baron de 

 Ferussac. These specimens have been polished, and have, most pro- 

 bably, been in the cabinet of Paris for twenty or thirty years; for, few 

 Uniones were admitted into the cabinet, at that time, without the loss 

 of their superficial protection. It is the ater (nobis), and, most pro- 

 bably, was taken from the neighbourhood of New Orleans, while in 

 possession of the French. The specimen described and figured in one 

 of my former memoirs, came from Port Gibson, below Natchez ; and I 

 subsequently received some from the vicinity of New Orleans and from 

 Claiborne, Alabama. I therefore, willingly yield the name to Lamarck.* 



* In the " American Conchology," No. V., Mr Say re-describes and re-figures the Unio 



