50 University of Michigan 
TRUNCILLA TRUNCATA Rafinesque, 1820 
Type locality: Ohio River. 
Truncilla truncata Rafinesque, ’20, p. 301. 
Unio elegans Wea, 31; p> $3, plo. £13: 
U. truncatus Raf.=U. donaciformis Lea, ’283=U. elegans ea, 
Conrad 344 ps 72: 
U. truncatus Raf.— U. elegans Lea, Ferussac, ’35, p. 27. 
Plagiola elegans -(1,ea), Simpson, ’I4, p. 307. 
Pl. elegans (Lea) =Tr. truncata Raf.=U. metaplata Raf., ’31; 
Vanatta, “I5, p. 553 (“types” examined). 
Pl. elgeans (Lea) =Tr. truncata Raf., Walker, ’16¢, p. 45; ’18¢, 
p. 179 (“if identifiable’). 
Amygdalonaias truncata (Raf.), Utterback, ’16, p. 148; Ortmann, 
Site, oy GyAOy 
This shell is small, has a “semi-triangular,’” somewhat quad- 
rate shape, the posterior end is truncate, and the margin and 
growth lines (vides) are curved (concave) behind. This is 
a satisfactory description of the species when compared with 
the only other “truncate” form of the Ohio (triquetra). 
U. donaciformis Lea, said to be also identical (Conrad), is 
closely allied, but the description of the shape does not fit it. 
The name 7runcilla truncata is not preoccupied by Unio 
truncata Spengler (1793), and thus truncata stands. 
TRUNCILLA DONACIFORMIS (Lea), 1828 
Type locality: Ohio. 
Unio nervosa Rafinesque, °20, p. 296, pl. 80, f. 8-10. 
Unio donaciformis Lea, ’28, p. 267, pl. 4, f. 3. 
Umno zigzag Wea, 720, p. 440, pl. 12, f. 19. 
U. nervosa Raf.=U. donaciformis Lea, Say, 734. 
U. nervosa Raf.=U. sigsag Lea, Conrad, ’34, p. 70. 
U. nervosa Raf. =U. sigzag Lea, Ferussac, ’35, p. 27. 
Plagiola donaciformis (ea), Simpson, 714, p. 308. 
The original description of the rays of nervosa, “Nervures 
flexweuses, concentriques, vermiculaires,” might suggest U. 
donaciformis, yet it surely is not quite exact, and the figure, 
