7CO UNIO 
Animal with the marsupium occupying the whole length of 
the outer gills; ovisacs not separated by a sulcus; gills long, 
inner a little the larger throughout, generally free their whole 
length from the abdominal sac; palpi enormous, wide, oval, 
slightly pointed behind, united two-thirds of their length te 
the mantle; mantle double on its edge; branchial openin; 
large. 
Unio porett Lea. 
Shell elongated subtrapezoidal, inequilateral, scarcely sub- 
solid, rather compressed, narrowed in front and the middle 
and wider behind, with a low, double posterior ridge, which 
ends in a wide, rather faint posterior biangulation; posterior 
slope obliquely subtruncate above; base line generally incurved 
at the middle, sometimes nearly straight, usually a little full 
behind the middle; beaks rather low but sharp, their sculpture 
consisting of a few doubly-looped ridges, the hinder loop 
heavier ; epidermis olive-green, sometimes clouded with tawny, 
often smoky, slightly rayed on the earlier growth, somewhat 
imbricated behind; left valve with two small pseudocardinals 
and two long, curved or nearly straight laterals; right valve 
with one pseudocardinal, sometimes with a faint second one 
above; beak cavities shallow, showing the dorsal pits; muscle 
scars shallow ; nacre dull purplish or purplish lead-color. The 
female shell seems to be a little fuller at the post-base than 
that of the male. 
Length 80, height 35, diam. 22 mm. 
Length 57, height 30, diam. 16 mim. 
South Texas; northeast Mexico. 
Type locality, Devil’s River, Texas; Rio Salado, New Leon, 
Mexico. 
Unio pope Lua, Pr. Ac. N. Sci. Phila., IX, 1857, p. 102; Jl. 
Ac, N. Sci. Phila., IV,. 1858, p. 372, pl. uxv1, fig. 197; Obs. 
VIII, 1860, p. 54, pl. Lxvi, fig. 197——SIMPSON, Syn., 1900, 
p. 738. 
Unio popei Sowrrsy, Conch. Icon., XVI, 1868, pl. LXxxt, fig. 
430. 
Margaron (Unio) popeii Lea, Syn., 1870, p. 57- 
