Occasional Papers of the Museum of Zoology 51 



if correct in this respect, does not support this view. Further, 

 the description says that the shell is larger behind (also shown 

 in figure), and that the borders are undulated (see also figure), 

 and these are characters which cannot be found in donacifonnis 

 by any means. Thus nervosa is not identifiable. 



Genus Plagioi^a Rafinesque, 18 19 



Type: Unio securis L^a. = Obliqiiaria lineolata Raf. 



Plagiola Rafinesque, '19, p. 426; '20, p. 302 (no type named) ; Herr- 

 mannsen, '47, p. 279 (type, Obliquaria interrupta Raf.) ; Agassiz, '52, 

 p. 42 (first species, Obliquaria lineolata Raf. ^ U. sccuris Lea) ; Simp- 

 son, '00, p. 603 (^type, U. securis Lea). 



Herrmannsen designated an unrecognizable species Obli- 

 qu-aria interrupta Raf. (see under Dysnomia brevidens) as the 

 type of Plagiola, and consequently Plagiola should be used in 

 the sense of Agassiz and Simpson. 



Plagiola lineolata Rafinesque, 1820 

 Type locality: Falls of the Ohio, at Louisville, Ky. 



Obliquaria {Plagiola) depressa Rafinesque, *20, p. 302, pi. 81, f. 5-7. 



Obliquaria {Plagiola) lineolata Rafinesque, '20, p. 303. 



Obliquaria {EUipsaria) ellipsaria Rafinesque, '20, p. 303. 



Unio securis Lea, '29, p. 437, pi. 11, f. 17. 



U. lineolaius Raf. = f/. depressus Raf. = L^ ellipsaria Raf. =^ [/. 

 securis Lea, Conrad, '34, p. 70. 



U. lincolafus Raf. = L'. depressus Rai. ^ sccuris Lea, Ferussac, '35, 

 p. 28. 



U. sccuris Lea=C/. depressus Raf., Lea, '38, p. 124. 



Plagiola lineolata Raf. ^ U. securis Lea, Agassiz, '52, p. 48. 



U. lincolatus (Raf.), Call, '00, p. 469. 



Plagiola securis (Lea) = Obi. depressa Raf., Simpson, '00c, p. 603; 

 '14, p. 305. 



PL lineolata (Raf.) = Obi. depressa Raf. = Obi. ellipsaria Raf. = 

 PI. securis (Lea), Vanatta, '15, p. 553 ("types" examined). 



PI. sccuris (Lea) = Obi. depressa Raf. = Obi lineolata Raf., Wal- 

 ker, '17c, p. 45; 'iSc, p. 179 ("if identifiable"). 



PI. securis (Lea) =F/. lineolata (Raf.), Utterback, '16, p. 150, foot- 

 note. 



Plagiola lineolata (Raf.), Ortmann, '18, p. 571. 



