AND OTHER FAMILIES. 91 



Lamarck cites Schroeter first. I have not an opportunity to examine 

 Schroeter's work. 



Unio nodulosa. This is a young individual of the ovata of Dono- 

 van, and no doubt the specimen cited never was out of Europe. The 

 ovala is emphatically an European shell, and has served, like the pic- 

 toriim, to which it has some resemblance, to make numerous species. 

 Lamarck's habitat (lake Champlain) is certainly an error. 



Unio varicosa. The specimen described by Lamarck is still in his 

 original cabinet. It is a young and bad specimen of the Alasmodonta 

 marginata (Say). From the description 1 formerly supposed it to be 

 ^las. undulata (Say). 



Unio granosa. The only specimen of this beautiful and distinct 

 species I saw in Europe, is in the Garden of Plants. It is unique in 

 the possession of disks completely covered with minute granular ele- 

 vations. 



Unio depressa. The specimen in the Duke de Rivoli's collection is 

 marked '-from Peru," and is a very different species from one which 

 I procured in Paris, marked by Lesson as depressa from New Holland. 

 Lamarck's description is so extremely vague, that it almost equally 

 well applies to both. The shell from Peru, of which I have several 

 specimens, is more transverse than that from New Holland, which I 

 presume should be considered the true depressa. 



Unio Virginiana. This is a bad specimen of radicdus, in the Duke 

 de Rivoli's collection. 



Unio luteolci. From the description and locality, I formerly sup- 

 posed this to be Say's cariosus. On examining the specimen at the 

 Garden of Plants, cited by Lamarck, I found it to be a true siliquoi- 

 deus of Barnes, which sometimes approaches the cariosus. There 

 must be an error in the locality given by Lamarck, as this species does 

 not inhabit the waters east of the Alleghany mountains. Lamarck's 

 name has precedence to that of Mr Barnes. 



Unio angusta. This is a distinct and interesting species. Its habi- 

 tat is unknown, and the only specimen I have seen is in the collection 

 at the Garden of Plants. 



Unio manca. I examined the original specimen in the cabinet of 



