0ONCHOL0GIC4I. WRITINGS. 13 



80 sp. Unio fleocus. [Toxolasma, ditto, 1821. j Shell thick 

 rounded, swelled, undulate below; outside subrugose, olive brown, 

 inside bluish ^\\i%. Length 5-6, diameter 1-2, axis l-6th of the 

 breadth. 



In the Kentucky river, rare, 1 or 2 inches, lamellar tooth well 

 curved, thick ; not serrulate. 



3. N. G. Babiosta. 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 3-5, diameter 2-5, axis 1-4 of the breadth. 



In the lower Ohio and Mississippi. Pine shell, with beautiful 

 nacre, 3 to 5 inches broad ; cardinal tooth striate, lamellar tooth 

 scabrous 1 Many uneven wrinkles inside. The U. sinuata Sp. 6T, 

 belongs to this section, .Barzoste 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.) Shell 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. 



^4 Sp. Unio diploderma, (Lampsilis ditto. 1822.) Shell thin 

 elliptical^ hardly swelled ; back hardly broader : surface a little 



