258. Mr. Barnes on the Genera Unio and Alasmodonta. 
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 following terms, viz. 
Datura Tatula, caule purpureo punctis viridibus asperso, 
pericarpiis spinosis erectis ovatis, foliis ovatis dentatis gla- 
bris. "4 
Datura Stramonium, caule viridi, pericarpiis spinosis 
erectis ovatis, foliis ovatis dentatis glabris. 
The facts that the coro] of D. Tutula is generally pale 
blue, or purple striped with deep purple inside, and that of 
- Stramonium white varying to cream colour, ought to be 
added by way of observation. 
he Datura from the Cape-of-Good-Hope, which has 
been lately called Tatwla, must, without doubt be consider- 
ed as entirely out of the question in this discussion, and 
even if the Eurepean and both the American plants, be ul- 
timately decided to be mere varieties, that ought unques- 
tionably to have another name. . 7 
Middletown, (Conn.) Jannary 1821. 
CONCHOLOGY. 
: —~— 
Art.—VIII.—On the Genera Unio and Alasmodonta; with 
Introductory Remarks : - H. Barnes, M. A. Mem 
ber of the New-York Lyceum of Natural History.* 
(Concluded from pa. 127.) | 
UNIO. 
** Cardinal teeth moderately thick, direct. 
OBSERVATIONS. ot 
Tue shells of this section are, in thick. 
C , In general, not very 
They have the beaks slightly elevated, or nearly flat, The 
[*Read before the Lyceum.] 
