On the Pumice of the Missouri. 21 



3. barbata. Id. p. 306. Ibid. Frond pendulous, smooth, 



terete, thick, branches diverging and fibrillose, articu- 

 lated below the apex. 



4. angulata Id. p. 307. Ibid. Frond pendulous, quadran- 



gular, angles sharp and scabrous. This species grows 

 in Massachusetts to the length of four feet. 



IV. Class. ATHALAMI. 



32. Lepraria. 



1. flava. Id. p. 330. Old bark of trunks. Rare. Crust 

 beautiful yellow. 



2 latebrarum. Id p. 331. On the earth, and stones in 

 shady moist places. Crust greenish gray, pulveru- 

 lent 



On the identity of the supposed Pumice of the Missouri, and 

 a variety of Amygd aloid found near the Rock? Mountains. 

 By Edwin James, M. D., Surgeon U. S. Army. Read 

 before the Lyceum, April 14, 1823. 



The light and porous stones, brought down the Missouri 

 by the annual floods, and which have been spoken of as Pumice 

 by Bradbury and others, differ from the ordinary varieties of 

 Pumice, in being less easily if at all fusible by the blow-pipe ; 

 in the absence of the fibrous structure ; and in many instances, 

 of the semi-vitrified aspect of that mineral. From the accom- 

 panying specimens, it will be perceived, that the Pumice of 

 the Missouri is, in all respects, similar to a substance collected 

 about the beds of Amygdaloid in the Trap formation, near the 

 sources of the Canadian river of the Arkansa. It occur; there 

 in detached masses, of various dimensions, from which it would 

 be easy to select specimens, exhibiting every intermediate 

 stage of gradation in specific gravity and colour, from the 



