41 
UNIO ICTERINUS. 
Plate VI. — Fig. 5. 
DESCRIPTION. 
Shell elliptical, moderately thick; anterior margin 
regularly rounded; posterior margin descending 
obliquely, and subtruncated at the extremity; beaks 
not prominent; umbonial slope very oblique, nearly 
rectilinear, angulated; epidermis smooth and polish- 
ed, olive yellow, clouded with brown on the margins; 
base slightly arcuated; nacre salmon coloured, iri- 
descent on the posterior margin. 
OBSERVATIONS. 
A species approaching that variety of U.purpureus, 
of Say, termed carinatus, by Lamarck; but I believe 
it to be quite distinct. It certainly does not resemble 
the purpureus of the same locality. 
Whilst at Augusta in the month of February, when 
the Savannah river had risen considerably above low- 
water mark, I found on the muddy shore opposite 
the town, numbers ofUnios, which had been recently 
taken by the muskrats. Amongst these were the 
two species mentioned above, U. angustatus , of 
Lea, abundance of U. congarceus, Lea, a remark- 
able variety of U. nasutus , Say, thick, and salmon 
coloured within; and a suborbicular species, very 
distinct from any other species I have seen. All the 
specimens of icterinus are more or less salmon co» 
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