ios) 
4 PILEUROPEMA 
KEY TO SPECIES OF PLEUROBEMA. 
Shell with a subvertical median row of nodules. 
Epidermis smooth, shining. @sopus. 
Epidermis cloth-like or silky, dull. compertum, cicatricosum. 
Shell not nodulous. 
Epidermis dark greenish-brown or blackish. 
Shell more or less rhomboid, 
Somewhat ‘elongated, blackish. brimleyt. 
Short, brownish. striatulum, modicellum, gibberum. 
Generally ovate, 
Rather thin, not inflated. patsaligense, simulans. 
Rather solid, subinflated. bulbosum, ravenelianum, 
hagleri, harperi, reclusum, nux, brumbyanum, 
perovatum, pinkstom. 
Elliptical, solid, much inflated. 
Subsolid, black. strodeanum. 
Solid, brown, rubellum, avellana, furvum. 
Subtriangular. 
Inflated, solid. curtum, showalteru. 
Somewhat compressed, nacre purplish. lenticulare. 
Nacre white. argenteum, fassinans. 
Epidermis yellowish, tawny or light brown, 
Rayless or feebly rayed. 
Beaks terminal or subterminal. decisum, 
chattanoogaense. 
Beaks not terminal. 
Oval or ellipttcal. hanleyanum, interventum, flav- 
idulum, swordianum, litum, georgianum, 
murrayanum. 
Rhomboid. 
Short. instructum, meredithii, breve, striatum. 
Longer. argenteum, conasaugense, pyriforme, 
amabile, estabrookianum. 
Triangular. altum, instructum, troschelianum, 
stabile, cor, verum, hartmanianum, crudum. 
