562 UNLO 
UNIO EPISCOPALIS Tristram. 
Shell rather large, elongated, subquadrate, solid, subcom- 
pressed, somewhat inequilateral ; beaks high but not very full, 
apparently sculptured with undulating plications; posterior 
ridge widely rounded, ending behind near the base; posterior 
end with a slightly oblique truncation above, rounded below ; 
base line straight or a little incurved in the middle; surface de- 
cidedly concentrically sculptured; epidermis black; pseudo- 
cardinals high, thick, subacute; laterals strong, elongated ; 
nacre brillant purple: pallial sinus deep ; anterior muscle scars 
deep; posterior scars well marked. 
Length 90-100, height 50-60, diam. 30-35 mm. 
Orontes and Jeontes rivers, Syria. 
Unio episcopalis TRistRAM, Pr. Zool. Soc. Lond., 1865, p. 544. 
—Koeet, Icon., VI, new ser., 1893, p. 89, pl. cLxxv, fig: 
LLI9.—SIMPSON, Syn., 1900, p. 694. 
Tristram calls this the prince of Oriental Unionide. It 
appears to be close to U. homsensis, but is much more squarely 
truncate behind and is more rounded at the post-basal termina- 
tion. 
Unio purreut Deshayes. 
Shell oblong, subrhomboid, rarely almost elliptical, having 
the dorsal and basal lines nearly parallel, inequilateral, convex, 
subsolid ; beaks only moderately full and elevated, their sculp- 
ture consisting of numerous broken, fine, corrugated ridges, 
which are sometimes more or less doubly looped and often 
arranged in imperfect zigzag patterns. This sculpture extends 
well out on to the disk, gradually changing to subnodulous con- 
centric ridges and lower down into delicate but well-marked 
growth lines that are strongest on anterior end of the shell. 
Posterior ridge low, sometimes feebly double and ending at 
end below the median line in an ill-defined biangulation ; epi- 
dermis yellowish or ashy-green to smoky-brown, often feebly 
raved: left valve with two sub-compressed, ragged pseudo- 
cardinals and two nearly straight laterals; right valve with one 
