Occasional Papers of the Musewm of Zoology 13 
Elliptio (Sphenonaias) liebmanni (Philippi) (1847), 
subspecies cuatotolapamensis, new subspecies 
Plate I, figs. 6, 7; plate III, fig. 22 (type) ; plate IV, figs. 20-25. 
Twenty specimens; including odd valves; from Rio San 
Javan: CEL vate). 
Shell of medium size, elongate subelliptical to subrhomboid, 
quite solid, convex, with posterior ridge well marked, sub- 
angular or often rounded and sometimes double; beaks weli 
anterior, sculpture (as interpreted from remains of smallest 
specimen) probably somewhat similar to that of FE. plexus, 
only not so oblique, and broken by the radial plications so as 
to give it an almost radial appearance (at least suggestive of 
some of the South American genera); anterior end evenly 
rounded or subangular just in front of lunule; posterior mar- 
gin gradually curved, sometimes quite markedly biangulate 
behind; basal line very slightly rounded to subsinuate, post- 
basal point but little elevated; epidermis (in older shells) dark 
brown to almost black, roughened to smooth and shiny, with 
fine, radiating striations (in younger shells with golden-yellow 
ground-color, almost completely obscured by diffuse olive-green 
rays); surface of shell usually marked by vertical furrows 
(which start high on the beaks and more or less disturb the 
beak sculpture), most prominent on and just behind the ante- 
rior slope, usually not extending more than 30 mm. ventrad 
from the beaks, and rarely by radiating, dorsally curved plica- 
tions as in &. plexus; left valve with two pseudocardinals, the 
anterior compressed, almost lamellar and very oblique, the 
posterior trigonal or compressed ventrally so as to be wedge- 
shaped, and two, elongate, almost straight laterals, of which 
the more ventral is better developed; right valve (II, 22) usu- 
ally with two, subequal, compressed, almost lamellar, and very 
oblique pseudocardinals, although sometimes the anterior is 
