UNITED STATES AND NORTHERN MEXICO. 21 



Hah. — Carter's Creek, J. Postell, and Factory Creek, Georgia. G. Ilallenbeck, 



My cabinet and cabinets of Mr. Postell and Mr. Ilallenbeck. 

 Diam. -9, Length 1-8, Breadth 29 inches. 



Shell smooth, quadrate, compressed, flattened at the sides, inequilateral, obtusely 

 biangular behind; substance of the shell rather thick, beaks a little prominent; 

 ligament rather long, thick and brown ; epidermis striate, shining towards the beaks, 

 reddish brown or dark brown, obsoletely rayed and with rather distant marks of 

 growth ; umbouial slope slightly raised and rounded ; posterior slope slightly raised, 

 with an obscure furrow from the beaks to the posterior margin ; cardinal teeth rather 

 thick, compressed, conical, crenulate and douljle in both valves; lateral teeth long, 

 lamellar, thick and curved; anterior cicatrices distinct and deeply impressed; pos- 

 terior cicatrices confluent and well impressed ; dorsal cicatrices usually a single well 

 impressed one in nearly the centre of the cavity of the beaks of each valve; cavity of 

 the shell shallow and wide ; cavity of the beaks very shallow and obtusely angular ; 

 nacre white or purplish and iridescent. 



Soft parts. — Branchial uterus . Branchice large, very thin, rounded below, inner 



ones rather the larger, free nearly the whole length of the abdominal sack. PaJ2ii' 

 large, transverse, suboval, united half way down the posterior edges. Mantle thin, 

 whitish. Branchial opening rather large, with rather lai'ge dark papillo3. Anal 

 opening rather large, with numerous very small brown papillse on the inner edges. 

 Super-anal opening very large, not united below, slightly colored on the inner edges. 

 Color of the mass whitish. 



Bemarlcs. — This belongs to the great complanatiis group, and certainly approaches 

 to the tj^pe, but it is more square in its outline, reminding one of hehes (nobis) 

 It is larger than the latter species and not so high in the posterior slope. The speci- 

 men figured is from Factory Creek, near Columbus, Georgia. From this stream they 

 are lighter in the color of the epidermis than those from Carter's Creek, and they are 

 usually of a light purple in the nacre, while those from Carter's Creek have a dark 

 brown epidermis and have a white nacre. A single one from Factory Creek out of 

 fifteen was inclined to salmon color. The lateral teeth are usually very stout and 

 the inferior duplicature is much thicker than the superior one, and is enlarged and 

 suddenly terminated at the posterior end. 



Unio Joxesii. pi. 54, fig. 1G4. 



Test:! Isvi, elliptica, subinflata, vald^ inwquilaterali, postici- obtuse angulatu; valrulis subtenuibus, antice 



crassioribus ; natibus prominulis, ad apices undulatis; epidermide lute:!, radiis interruptis; dentibus 



cardinalibus parviusculis, ereotis, conicis; lateralibus sublongis, lamcllatis rectisque; margarita vel alba 



vel salmonis colore tincta et valdii iridescente. 



Shell smooth, elliptical, slightly inflated, very inequilateral, obtusely angular 



I 



