4 University of Michigan 



follows : the use of such a name depends upon whether it 

 could be identified by descriptions published prior to any other 

 recognizable name for the same species. That it can be recog- 

 nized from the type or other specimens of the author does not 

 entitle his name to acceptance unless the published descrip- 

 tion is adequate. 



It would seem clear from this that Unio violaceus Speng. 

 must be considered to date from 191 3 and not from 1793 and 

 that consequently it is a synonym of U . complanatus Dill. 



IV 



I lemilastena was proposed as a generic term by Agassiz 

 in 1852. and the type is expressly stated to be Unio dehisccns 

 Say ("earlier well described as Hcmilastena lata by Rafines- 

 que"), for this reason and not because Hemistena Raf., 1820, 

 is a contraction of Hemilastena, which is entirely immaterial 

 as the two names are quite different, it is clearly a synonym 

 of Lastena Raf. as stated by Frierson (Naut., XXVII, 1914, 

 p. 8), and the genus of which Alasmodonta ambigua Say is 

 the type will consequently be known as Simpsoniconcha 

 Frierson. 



V 



In 1 83 1 Rafinesque, in the Continuation of his Monograph, 

 p. 3, described a new species of Unio from the Cumberland 

 River as follows : 



"Unio rimosus, (Bnrynia riniosa, 1823). Shell elliptic, 

 thick, thinner, broader and rimose behind; surface olivaceous 

 nearly smooth, inside bluish white. Length 2/3, diameter 1/6, 

 axis yi oi length. 



"In the Cumberland river, rare, small lYz inch. Resem- 

 bling some Amblemas, but evidently transversal, cardinal 

 tooth crenulate, lamellar smooth, short, nearly horizontal, but 



