52 The Shell-Collector’s Handbook. 
UNIO TUMIDUS, PHILIPPSSON. 
SHELL ovato-oblong, wedge-shaped, swollen, moderately 
thick, solid, brown, often tinged with green in lines of 
growth ; epidermis smooth; umbones prominent, rugose, 
excentric; lunule lanceolate, narrow; ligament short, 
thick, and prominent ; anterior side rounded and sloping 
towards the front; posterior side produced and atten- 
uated so as to become wedge-shaped ; anterior teeth high, 
conical and strong. Animal greyish. Mantle bordered 
with brown ; upper orifice elongated and of a brown colour ; 
lower orifice pale grey. Length of shell 3 inches; width 
13 inches. 
Habitat —Canals, ponds, and slow-running rivers. 
v. radiata (Colb): Shell thinner; epidermis green- 
ish with yellow rays which are interrupted by bands of 
the same colour running transversely across the shell; 
posterior side more compressed above ; hinge line nearly 
straight. 
v. ovalis (Mont.): Shell wedge-shaped, dark olive- , 
brown; anterior side broader, abruptly truncate; lunule 
broad, deep, oblique. (=Mya ovalis. Montagu, Test. 
Brit. pp. 34 and 563.) 
UNIO PICTORUM, LINN. 
SHELL ovato-oblong, wedge-shaped, ventricose, solid, 
greenish-yellow, marked with brown in lines of growth, 
and green-coloured towards the posterior margin; pos- 
terior side not wedge-shaped, but produced into a bluntly 
truncated beak; anterior side rounded; umbones not so 
prominent nor so rugose as in U. tumidus; lunule long, 
