44 University of Michigan 
‘determination of the so-called Rafinesque-Poulson “type” of 
stegaria. 
“The Rafinesque-Poulson shell is stated to be of the var. 
tuberculata Raf. It is an ivrorata of the usual size and green- 
ishecolon | (al wens) 
Genus OpovariA Rafinesque, 1819 
Type: Unio retusa Lam. 
Rotundaria Rafinesque, ’20, p. 308 (no type named) ; Herrmannsen, 
"47, p. 407 (type, Obliquaria subrotunda Raf.); Simpson, ’o0, p. 794, 
as a subgenus of Quadrula (type, Obliquaria tuberculata Raf.) ; Ort- 
mann, ’I2, p. 257, as a genus (type, the same). 
Obovaria Rafinesque, ’19, p. 426; ’20, p. 310 (no type named); Her- 
mannsen, °47, p. 132 (type, Obovaria obovalis Raf., not recognizable) ; 
Agassiz, 52, p. 46 (type, U. retusa Lam., congeneric with Obliq. sub- 
rotunda Rat.); Simpson, ’00, p. 498 (type, U. retusa Lam.). 
“Rafinesque proposed Obovaria in 1819 with a diagnosis but 
no type or recognizable species, since none of those mentioned 
as belonging to the genus had then been described. The diag- 
nosis clearly indicates a certain assemblage of Uniones which 
had not before been segregated, viz., those with a rounded 
shell with the axis (7. e., the vertical from the beaks) nearly 
median; such as the species subsequently included by Simpson 
in Obovaria, Theliderma, and Rotundaria. For some part of 
this assemblage the genus defined in 1819 is valid. 
“In 1820 Rafinesque further limited the genus, describing 
six species, one of which, U. obovalis, was designated type by 
Herrmannsen in 1847; this species has never been identified, 
and is believed to be unrecognizable. In 1852 another of the 
original species, Ob. torsa, was selected as type by Agassiz. 
This type has been accepted by Simpson, 1900, and by subse- 
quent authors, whose action is here endorsed. 
“As the type of Rotundaria is congeneric with O. torsa, 
that name becomes a synonym of Obovaria, being one year 
later in’ date? i(Hs A. “P2) 
