Poe NE rus. 
Wers DI FEBRUARY, 1898. No. 10. 
UNIO (LAMPSILIS) AMPHICHENUS, N. Sp. 
BY LORRAINE S. FRIERSON. 
Shell large, oblong oval, thin, slightly inflated, gaping for one- 
half its length at the anterior and basal part, and at the upper part 
of the posterior end, and covered with a shining, black or brownish 
epidermis which is decidedly wrinkled in places; growth lines 
strong and irregular ; beaks but slightly prominent; hinge line 
evenly curved; hinge teeth but feebly developed, there being a 
single, compressed, rather sharp cardinal in the left valve of the 
young shell which becomes blurred and shows a tendency to split 
up in the older shells, and two rather short, faint laterals, the inner 
of which is the stronger; these being placed at the extreme poste- 
rior end of the hinge plate, with one cardinal, and sometimes a 
faint one above it, and a single, compressed, short lateral in the 
right valve; laterals ending abruptly at the posterior end, with the 
inner edges slightly curved upwards; area between the teeth nar- 
row and rounded; muscle scars distinct, and quite deep for so thin 
a shell; posterior retractor scar completely united with the adduc- 
tor, dorsal scars to the number of five or six extending in a row from 
the cavity of the beaks just behind their greatest projection towards 
the anterior base; pallial line showing a tendency to break up into 
several lines, and distinct traces of a posterior sinus; nacre clouded, 
varying from deep violet to bluish and white. 
Length 106, height 63, diam. 36 mm. 
Habitat, Sabine, River at Logansport, Louisiana. 
