go2 QUADRULA 
are from a shell taken in the Usumacinta River, Guatemala, 
and sent to the National Museum by von Ihering. The Na- 
tional Museum has still larger specimens from Tabasco, Mex- 
ico. It is shorter, more inflated, and solider than the nearly 
allied rugososulcata and the pallial line is closer to the shell 
border than it is in that species. 
QUADRUILA RUGOSOSULCATA (Lea). 
Shell elongately triangular, subequilateral, rather inflated 
and solid, with a sharp, double posterior ridge, the lower ridge 
decidedly angled, the upper less pronounced; truncated above 
and rounded below in front; the base line nearly straight ; 
beaks high and moderately full, their sculpture consisting of 
rather fine bars running nearly parallel with the growth lines; 
surface closely and rather sharply, concentrically sculptured 
throughout; epidermis dirty greenish-brown, darker above, 
somewhat wrinkled; left valve with two stumpy, radial pseudo- 
cardinals and two laterals, the lower larger; the hinge plate 
flattened under the beak and narrowed behind; right valve with 
one pseudocardinal, a small tooth in front of it and a vestigial 
one behind it; beak cavities rather deep, scarcely compressed ; 
anterior scars very deep; posterior scars large and impressed ; 
pallial line deep and broken, distant from the edge of the shell 
in front ; nacre bluish-white, thicker in front. 
Length 80, height 57, diam. 35 mm. 
Central America. 
Unio rugososulcatus. Lex, Pr. Ac. N. Sci. Phila., X, 1866, p. 
235 ji Aco NSci- Phila.,- Vij 1868, sp. 260, pl aamciy tie eee 
Obs:; STL 1 860,2p- 26, pr xexociy ieee 
Margaron (Unio) rugososulcatus LeA, Syn., 1870, p. 35. 
OQuadrula rugososulcata SIMPSON, Syn., 1900, p. 794. 
A fine species, the type being in the Lea Collection. Signor 
Paz sent Lea two shells, one of which Lea kept and the other 
he returned. The locality “Central America” is written inside 
the left valve of Iea’s shell. It is longer and less inflated than 
O. spheniopsis, to which it seems to be nearly related and is 
not so heavy as that species. 
