CONCHOLOGICAL WRITINGS. 73 
80 sp. Unio flexus. [Toxolasma, ditto, 1821.] Shell thick 
rounded, swelled, undulate below; outside subrugose, olive brown, 
inside bluish white. Length 5-6, diameter 1-2, axis 1-6th of the 
breadth. 
In the Kentucky river, rare, 1 or 2 inches, lamellar tooth well 2 
curved, thick; not serrulate. 
3. N. G. Barrosta. Form of Scalenaria, lamellar tooth curved, 
and not obliqual, as in Sintoxia, shell transversal, triangular. 
81. Sp. Unio ponderosus. (Bariosta ditto, 1820.) shell very 
thick and heavy, oval triangular, rounded before, curved slope 
behind, with an oblique ridge ending to a point, a sinus next to it; 
outside rough and blackish; inside incarnate, iridescent, uneven. 
Length 38-5, diameter 2-5, axis 1-4 of the breadth. 
In the lower Ohio and Mississippi. Fine shell, with beautiful 
nacre, 3 to 5 inches broad; cardinal tooth striate, lamellar tooth 
scabrous! Many uneven wrinkles inside. The U. sinwata Sp. 67, 
belongs to this section, Bariosta having a similar lamellar tooth: but 
it is broader, more elliptical, without ridge, and white inside; the 
sinus is also more central. 
82 sp. Unio vittatis (Lampsilis? vittata.—1818.) Shell oval, 
swelled, rather thin, broad subalate and subtruncate behind with two 
or three oblique ribs longitudinal, rounded and rugose before, sides 
smooth, outside olivaceous, radiated with narrow straight greenish 
rays, bluish white inside. Length 3-4, diameter one half, axis one 
third of breadth. 
In Green river, 3 inches broad or more. Very near my Lampsilis 
Fasciola, sp. 26:—but it is larger, rounder, with straight rays. 
Cardinal tooth crenulate, lamellar tooth not flexuose, but well 
curved in the right valve ; short, compressed, truncate behind. 
83 sp. Unio montanus, (Eurynia montana, 1823.) Skell thin, 
elliptical, compressed, behind broad a little winged, end truncate, 
outside nearly smooth brown, a little laminated and fulvous around, 
inside bluish. Length one half, diameter and axis 2-5 of breadth. 
In the streams of the Alleghany and Cumberland mountains. 
About 2 inches. Lamellar tooth very long, nearly straight, a sinus 
above it. 
84 Sp. Unio diploderma, (Lampsilis ditto. 1822.) Shell thin 
elliptical, hardly swelled; back hardly broader: surface a little 
