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 rimosns is not identifiable.'' (H. 

 A. P.) 



Thus, the name riwosus for the species cannot be used, and 

 consequently also Lcmiox 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 localvty: Unknown. 



Unio phitcolus Rafinesque, '31, p. 3. 

 Unio conradicus Lea, '34, p. 63, pi. 9, f. 23. 

 Unio conradicus Conrad, '38, p. 87, pi. 47, f. 3. 

 Medionidus conradicus (Lea), Simpson, '14, p. 247; Walker, 'i8c, 

 p. 70. 



Medionidus plateohis (Raf.) ^= conradicus Lea. Ortmann, '18, p. 575. 



The original description of U. plateohis 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 Ligtunia (trabalis and the iris group), or a young 

 Icptodon, or a flat, young dUataia. 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 plateohis is not identifiable. 



