88 ON THE NAIADES, 



Unio ligamentina. The specimen in the Garden of Plants is the 

 U. crassus of Say. 



Unio obliqua. in the same collection is the U. undatus of Barnes. 



Unio retusa. This is the U. torsus (Rafinesque). The locality given 

 is Nova Scotia ; the correctness of which I doubt much. It is, as yet, 

 known to exist only in our western waters. 



Unio rarisulcata. The specimen in the Garden of Plants is the 

 complanatus (Soland.), jmrpureus of Say. 



Unio coardata. The specimen in the collection of the Duke de 

 Rivoli is the complanatus (Soland. ). The observation of Lamarck, that 

 " it is the analogue of our U. margaritifera," (he ought to have said 

 elongala, for he does not use the name of margarilijera) must be an 

 error. The American shell, described by Barnes as Masmodonta ar- 

 cuata, is the unquestionable analogue of the true Mya margaritifera 

 (Linn.), and a very different shell, not having a lateral tooth, and 

 belonging to Schumacker's genus Margaritana (Say's Jllasmodonta). 



Unio purpurascens. This is also a complanatus, in the museum of 

 the Garden of Plants. 



Unio radiata. The specimen at the Garden of Plants is the true 

 radiatus. The Unio ochraceus (Say), given as a synonyme, is a very 

 distinct species. 



Unio hrevialis. The specimen at the Garden of Plants resembles so 

 closely the U. liftoralis, that I am induced to believe it never came 

 from the Isle of France, and that it is of European origin. That in 

 Baron de Ferussac's cabinet is certainly an old littoralis. The shell 

 figured by Crouch, under the name brevialis, is entirely distinct. 



Unio rhombula. The specimen now in the cabinet of the Dukede 

 Rivoli* is a young and bad specimen of the complanatus, and certainly 

 from thfc United States, and not Senegal. Var. b, in the cabinet of 

 Valenciennes, 1 did not see. 



ater, under the name of U. lugubris, alleging that the name ater is " preoccupied by Nilsson 

 for a very distinct species." Mr S. does not seem to be aware, that Nilsson's ater is only a 

 variety of U. Batava, of Maton and Racket ; and, therefore, could not affect my claim. We 

 must both yield to the prior claim of Lamarck. 



* I ought to say that the Duke keeps the cabinet of Lamarck intact, as much as possible, and, 

 therefore, the shells quoted may be relied on as being the same as described by Lamarck. 



