14 -University of Michigan 



Genus Quadrui^a Rafinesque, 1820 

 Type: Obliquaria (Quadritla) quadrula Raf. 



Quadrula Rafinesque, '20, p. 305 (as subgenus of Obliquaria) ; Simp- 

 son, 'OQC, p. 765 (as genus), '14, p. 811; Ortmann, '12, p. 250; Walker, 

 'i8c, p. 43. 



The subgenus Quadrula was introduced by Rafinesque for 

 nine sj^ecies, 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 ('52, p. 48) elevated Quadrula to the rank of a 

 genus, with eight species. No type was named, but among 

 the species is U. rugosns 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 ('00*^ and '14) accepts Quadrula as genus, desig- 

 nating Obliquaria {Quadrula) metanevra Raf. as type. 



Ortmann ('12) restricts Quadrula with metanevra as type, 

 and so does Walker ('18^). 



According to the Code, Quadrula quadrula Raf. must be the 

 "ipso facfo" type. The subsequent designation (by Simpson) 

 of metanevra is against the rules. 



H. and A. Adams having made Theliderma a synonym of 

 Quadrula, 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. 



