14 University of Michigan 
Genus QUADRULA Rafinesque, 1820 
Type: Obliquaria (Quadrula) quadrula Raf. 
Quadrula Rafinesque, ’20, p. 305 (as subgenus of Obliquaria) ; Simp- 
son, 00°, p. 765 (as genus), ’14, p. 811; Ortmann, ’12, p. 250; Walker, 
18°, p. 43, 
The subgenus Quadrula was introduced by Rafinesque for 
nine species, with no type named, but among them Obliquaria 
(Quadrula) quadrula, which should be the type (Rules, Art. 
30, I. (d)) by absolute tautonymy. 
Swainson (’40, p. 378) introduced the subgenus Theliderma 
for seven species, among them the type of Quadrula (lachry- 
mosa— quadrula), but no type was named. 
Agassiz (752, p. 48) elevated Quadrula to the rank of a 
genus, with eight species. No type was named, but among 
the species is U. rugosus Bar.=Q. quadrula, 
H. and A. Adams (’58, p. 497) make Theliderma Sw. a 
synonym of the subgenus Quadrula Raf., giving 17 species, 
but no type. Among the species are lachrymosa and asper- 
rima, both = quadrula., 
Simpson ('0o° and 714) accepts Quadrula as genus, desig- 
nating Obliquaria (Quadrula) metanevra Raf. as type. 
Ortmann (712) restricts Quadrula with metanevra as type, 
and so does Walker (’18°). 
According to the Code, Quadrula quadrula Raf. must be the 
“ipso facto” type. The subsequent designation (by Simpson) 
of metanevra is against the rules. 
H. and A. Adams having made Theliderma a synonym of 
OQuadrula, and Simpson (00°, p. 775) having selected for the 
section Theliderma the species lachrymosa (= quadrula) as 
type, Theliderma becames a synonym of Quadrula. ‘Thus, the 
genus and section in which quadrula stands must retain the 
name Quadrula. 
