58 University of Michigan 
esque’s measurement of diameter was an error; in cases where 
a figure is present to serve as guide for such corrections they 
are justified. Otherwise nobody has a right to change an 
author’s express statements to make them conform to a theo- 
retical identification. Unio rimosus is not identifiable.” (H. 
As sles) 
Thus, the name rimosus for the species cannot be used, and 
consequently also Lemiox for the genus is not available. Since 
the species should be placed in a separate genus (see Ortmann ) 
a new name was needed, and Ortmann (1. c.) has proposed 
that of Conradilla. 
MEDIONIDUS CONRADICUS (Lea), 1834 
Type locality: Unknown. 
Unio platcolus Rafinesque, ’31, p. 3. 
Unio conradicus Lea, 34, p. 63, pl. 9, f. 23. 
Unio conradicus Conrad, °38, p. 87, pl. 47, f. 3. 
Medionidus conradicus (Lea), Simpson, “14, p. 247; Walker, ‘18¢, 
p. 70. 
Medionidus plateolus (Raf.) = conradicus Lea, Ortmann, ’18, p. 575. 
The original description of U. plateolus Raf. is entirely 
insufficient to recognize this species. The chief characters are: 
general shape (elliptic-lanceolate and very compressed), small 
size (2 inches), and color (brown, inside bluish). They apply 
to conradicus, but also to a number of other species, chiefly of 
the genus Liguimia (trabalis and the iris group), or a young 
leptodon, or a flat, young dilatata. Besides, the shell is called 
attenuate and subacute behind, which does not fit conradicus 
very well, and the characteristic wrinkles of the posterior 
slope in this species and the rays, which generally are distinct, 
have not been mentioned. Thus plateolus is not identifiable. 
