UNIO 537 
with two pseudocardinals, the upper small, and one lateral; 
nacre bluish-white, a little iridescent behind, thickened in front. 
Length 60, height 27, diam. 15 mm. 
Length 55, height 28, diam. 15 mm. 
Central Europe. 
Unio elongatula C. PFEIFFER, Nat. Deuts. L. and S. Moll., II, 
1825, p. 35, pl. vul, figs. 5, 6. 
Unio elongatulus RossMAssuER, Icon., IT, 1835, p. 23, pl. 1x, 
figs rs2) Ale 18445. 27, pl. ivi, fig. 757: V1;\1870; p. 42, 
pl. cLxu, figs. 1644, 1645——Kustrr, Conch. Cab. Unio, 1854, 
p. 104, pl. xxvutt, figs. 4, 5—Drouer, Nay. Fr., IT, 1857, p. 
gI, pl. vi, fig. 2—SowerBy, Conch. Icon., XVI, 1868, pl. 
LXXXV, fig. 451.—Srmpson, Syn., 1900, p. 684. 
Margarita (Unio) elongatus Lea, Syn., 1836, p. 37. 
Margarita (Unio) elongatulus Lea, Syn., 1838, p. 24. 
Margaron (Unio) elongatulus Lea, Syn., 1852, p. 37; 1870, p. 
59- 
More delicate and compressed, smaller and a trifle more bi- 
angulate behind than U. pictorum, yet it may be only a variety 
of it. The beak sculpture is not so nodulous and the pseudo- 
cardinals of the left valve are more distinct than in Linnzeus’ 
species. 
UnIo TUMIDUs Retzius. 
Shell long ovate, being wide in front and gradually narrowed 
and drawn out to a point on the median line behind, subsolid 
to solid, subinflated, inequilateral; beaks moderately full and 
high, their sculpture consisting of uneven nodulous or sub- 
nodulous ridges, which are corrugated and generally doubly 
looped ; posterior ridge subangular but not high, placed near 
the dorsal line of the shell; surface almost smooth, with scat- 
tered growth lines; epidermis bright and shining, greenish- 
yellow, yellowish-green, ashy or reddish-brown, often some- 
what rayed; left valve with two compressed, ragged pseudo- 
cardinals and two delicate, nearly straight laterals; right valve 
with one pseudocardinal, with sometimes a vestige of another 
