258 Mr. Barnes on the Genera Unio and Alamnodonla. 



others whose attention has been particularly turned to the 

 subject for some years past. Under this impression I shall 

 venture to suggest an emendation of the specific characters 

 of the plants in question, in the followinj^ terms, viz. 



Datura Tatula, caule purpureo punctis viridibus asperso, 

 pericarpiis spinosis erectis ovatis, foliis ovatis dentatis gla- 

 bris. 



Datura Stramonium, caule viridi, pericarpiis spinosis 

 erectis ovatis, foliis ovatis dentatis glabris. 



The facts that the corol of D. Taiula is generally pale 

 blue, or purple striped with deep purple inside, and that of 

 D. Stramonium white varying to cream colour, ought to be 

 added by way of observation. 



The Datura from the Cape-of-Good-Hope, which has 

 been lately called Tatula^ must, v^^ithout doubt be consider- 

 ed as entirely out of the question in this discussion, and 

 even if the European and both the American plants, be ul- 

 timately decided to be mere varieties, that ought unques- 

 tionably to have another name. 



Middletozon, (Conn.) Jannary 1821. 



CONCHOLOGY. 



j\^RX. — VIII. — On the Genera Unio and Alasmodonta ; with 

 Introductory Remarks : by D. H. Barnes, M. A. Mem- 

 ber of the Mw-York Lyceum of Natural History.^ 



(Concluded from pa. 127.) 



UNIO. 



** Cardinal teeth moderately thick, direct. 



OBSERVATIONS. 



The shells of this section are, in general, not very thick. 

 They have the beaks shghtly elevated, or nearly flat. The 



r*Read before the Lyceum.] 



