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 donaciformis 
by any means. Thus nervosa is not identifiable. 
Genus PLAcioLA Rafinesque, 1819 
Iyvpe: Unio securis Lea == Obliquaria 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. securis Lea) ; Simp- 
son, ‘00, p. 603 (type, U. securis Lea). 
Herrmannsen designated an unrecognizable species Obli- 
quaria 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, pl. 81, f. 5-7. 
Obliquaria (Plagiola) lineolata Rafinesque, ’20, p. 303. 
Obliquaria (Ellipsaria) ellipsaria Rafinesque, ’20, p. 303. 
Unio securis Lea, ’20, p. 437, pl. 11, f. 17. 
U. lineolatus Raf.=U. depressus Raf.=U. ellipsaria Raf.=U. 
securis Lea, Conrad, ’34, p. 70. 
U. lineolatus Raf. =U. depressus Raf.=securis Lea, Ferussac, ’35, 
p. 28. 
U. securis Lea=U. depressus Raf., Lea, ’38, p. 124. 
Plagiola lineolata Raf.=U. securis Lea, Agassiz, ’52, p. 48. 
U. lineolatus (Raf.), Call, ’00, p. 4609. 
Plagiola securis (Lea) = Obl. depressa Raf., Simpson, ’o00*¢, p. 603; 
"14, Pp. 305. 
Pl. lineolata (Raf.) = Obl. depressa Raf.= Obl. ellipsaria Rat. = 
Pl, securis (Lea), Vanatta, 715, p. 553 (“‘types” examined). 
Pl. securis (Lea) = Obl. depressa Raf. = Obl. lineolata Raf., Wal- 
ker, °17°, p. 45; 718¢, p. 179 (“if identifiable”). 
PI, securis (Lea) = Pl. lineolata (Raf.), Utterback, ’16, p. 150, foot- 
note. 
Plagiola lineolata (Raf.), Ortmann, 718, p. 571. 
