280 NEW UNIONIDJE, MELANIDiE, ETC., 



Shell smooth, transverse, subcylindrical, emarginate at the base, very inequilateral, 

 somewhat compressed, flattened at the sides, truncate behind, rounded before ; valves 

 very thin, semitransparent; beaks a little prominent; epidermis yellowish olive; 

 cardinal teeth acicular, rather long and oblique ; lateral teeth long, lamellar and 

 nearly straight ; nacre wbite and iridescent. 

 Proc. Acad. Nat. Sci. 1866, p. 133. 



mih.—Sl?Lm, C. M. Wheatley. 



My cabinet and cabinet of Mr. Wheatley. 

 Diam. -5, Length I'l, Breadth 2-3 inches. 



Shell smooth, transverse, subcylindrical, emarginate at the base, very inequilateral, 

 somewhat compressed, flattened at the sides, truncate behind, rounded before ; sub- 

 stance of the shell very thin, semitranslucent ; beaks small, somewhat pointed and a 

 little prominent; ligament very thin and light brown ; epidermis yellowish olive, with- 

 out rays or obscurely rayed and with distant marks of growth ; umbonial slope slight- 

 ly raised and rounded ; posterior slope narrow elli]3tical, with a rather high carina ; 

 cardinal teeth acicular, rather long and oblique; lateral teeth long, lamellar and 

 nearly straight ; anterior cicatrices confluent and very slightly impressed; posterior 

 cicatrices confluent and scarcely perceptible ; dorsal cicatrices placed directly over the 

 centre of the cavity of the beaks ; cavity of the shell rather shallow and wide ; cavity 

 of the beaks very shallow ; nacre white, inclining to yellow and very iridescent. 



Remarlcs. — Mr. Wheatley kindly sent me his three specimens for examination and 

 description. The largest, 2^ inches wide, is evidently mature — the other two are 

 younger. It is a very thin, delicate species, with very remarkably thin, slender, 

 cardinal teeth. The lateral teeth are also thin and long, and in the left valve there 

 is a disposition to have a triple termination. In outline this species is almost identi- 

 cal with 'Poe?/anits (nobis) from Mexico, but that is a much thicker shell and has very 

 different cardinal teeth. In the youngest specimen before me the elevated carina is 

 greenish and has a few obscure rays. lu outline it is quite different from Peguensis, 

 Anth., being much more transverse, 



Unio asperulus. pi. 38, fig. 94, 



Testa plicata, elliptica, inajquilaterali, postice subbiangulata, antice rotundata ; valvulis subtenuibus ; 

 natibus subprominentibus, ad apices uudulatis ; epidermide viridi-oliva, obsolete radiata ; 

 dentibus cardinalibus lamellatis, parum obliquis, in dextro dupllcibus ; lateralibus sublongis, 

 lamellatis subcurvisque ; margarita cseruleo et valde iridescente. 



Shell plicate, elliptical, inequilateral, subbiangular behind, rounded before ; valves 

 rather thin ; beaks a little prominent, folded at the tips ; epidermis olive-green, 

 obscurely rayed; cardinal teeth lamellar, somewhat oblique, double in the right 



