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I. TRIBE.— "CNIO. 



1. N. G. Epioblasma. Differs from Amblema and Ellipsaria hy 

 lamellar tooth obliqual, divergent towards the bacli and straight. 

 .A,xis nearly terminal. The Unio or Amblema torulosa. Sp. 55, 

 perhaps belojigs here also. 



76. Sp. Unio biloba or Epioblasma biloba, discoTered 1821. 

 Elliptical, both ends rounded, back convex, belly bilobed, sides 

 rugose, more or lessgibbose, swelled before, greenish brown outside, 

 bluish white inside. Breadth 2-3, diameter 2-5 of. the length. 

 Var. 1. Pallida not greenish, rufescent, a little longer. 

 In Green river and Kentucky river, about 3 inches long. Remark- 

 able species, very rare, summits prominent, teeth striated, the lamel- 

 lar short, reaching only to the middle. 



2. N. G. ToxoLASMA, Differs from Amblema, Plagiola and Sin- 

 toxia, by lamellar tooth not obliqual but arched parallel with the 

 back, axis nearly terminal, general form rounded, back curved. 



7*7. Sp. Unio cyclips. ( Toxolasma cyclips. — 1820.) Shell thick 

 rounded-elliptical, swelled subglobose, subrugose and yellowish out- 

 side, incarnate inside. Breadth 6-1, diameter 4-8 of the length. 

 Axis 1-lOth. 



Yar. I. Fuscata. Larger, brown outside, and nearly smooth, 

 whiter inside, longer lamellar tooth. 



Var. II. Lutescens. Yellow outside, bluish, white inside. 

 River Ohio and Mississippi 2 to 4 inches, beautiful nacre, lamellar 

 tooth carinate, serrulate as in many other species. It is said that 

 this is the U. abruptus of Say. I cannot see any thing abrupt in it ; 

 my name means Bound Ellipsis. 



78 sp. Unio cinerescens (Toxolasma ditto. — 1820.) Shell thick, 

 rounded oboval, a slight posterior obliqual ridge, nearly smooth and 

 cinerescent brown outside, bluish white inside. Breadth 8-9, diameter 

 5-9 of the length. Axis l-9th. 



River Ohio and Kentucky. About 2 inches, cardinal tooth much 

 striated, lamellar not Serrulate. 



79 sp. Unio lividus, {Toxolasma do. 1822.) Shell elliptical 

 swelled not thick, outside subrugose, brown, inside livid purplish. 

 Length 8-4, diameter 3-8, axis 1-4 of the breadth. 



Iu.Rockcastle river, exceedingly rare Size only one inch, lamel- 

 lar tooth long, thin curved, not serrulate. 



