698 UNIO 
Unio folliculatus Lea, Tr. Am. Phil. Soc., VI, 1858, p. 38, pl. 
x1, fig. 33; Obs., I, 1838, p. 38, pl. x1, fig. 33—HANLEy, 
siv. Shells, 1843, p. 204, pl. xxi, fig. 55.—CHENu, II. 
Conch., 1858, pl. xxii, figs. 4, 4a, 4b—lKustrr, Conch. Cab. 
Unio, 1861, p. 202, pl. Lxvu, fig. 4—Sowrrby, Conch. Icon., 
XVI, 1868, pl. xc, fig. 493.—SIMPSON, Syn., 1900, p. 737. 
Margarita (Unio) folliculatus Lka, Syn., 1836, p. 34; 1838, 
p23: 
Margaron (Unto) folliculatus Lea, Syn., 1852, p. 35; 1870, p. 
Side 
Umo attenuatus Lea, Pr. Ac. N. Sci. Phila., II, 1872, p. 157; 
JioAc. Ne Ser. Phila; VI, 1874-p.414 pl xive es 26 One. 
XIII, 1874, p. 45, pl. xiv, fig. 38.—Simpson, Syn., 1900, p. 
730. 
Umo. exacutus Lea, Pr.cAc N. Scr Phila. i 1872p. 1G. 
Ji Ac. No Set. Phila, VBL 1874 plas, pl xy hie 23) Obss 
MUL 1874.9. 40; pl ave. Aa 
Unio rostellum Lea, Pr. Ac. N. Sci. Phila., II, 1872, p. 160; 
Jl: Ac. Ser Philay Villian 745 44 plex ie 4 Ops 
XI, 1874, p. 48, pl. xv hig: An. 
After bestowing additional study on the puzzling forms of 
this group, I confess that I can see no valid reason why Unio 
attenuatus should be kept separate from U. folliculatus. ‘The 
type of U. rostellum is quite a thin shell, that of U. attenwatus 
is a little more solid, while U. folliculatus and exacutus are 
more solid. But there seems to be every variety in the way of 
intermediates and the general form of all is the same. 
UNIO SHEPARDIANUS J[ea. 
Shell excessively elongated, usually more or less arcuate, 
rarely straight, generally but not always, higher in front, sub- 
solid, subcompressed to subinflated, very inequilateral; beaks 
compressed and but little elevated above the dorsal line, their 
sculpture apparently strong, slightly doubly-looped ridges; 
posterior ridge well developed, subangular or narrowly round- 
ed, sometimes double below, ending behind in a point or bian- 
gulation near the base of the shell; surface irregularly, concen- 
trically sculptured; epidermis greenish and often feebly rayed 
