FRESH WATER AM) LANS BHELLS. L'?.") 



A single specimen only is under my inspection, and tliis is much eroded on the superior 

 portion, leaving only false beaks. It is not, of course, possible to say whether the tips 

 arc undulate or not. 



Unio succissus. PI. XXI. Fig. 32. 



Testa Isevi, sublriangulari, subcompressri, insequilaterali, tenebroso-fuscd; valvulis subcrassis; natibus 

 subprominentibus ; dentibus cardinalibus magnis; latercdibua parvis subreclisque; margaritd purpurea il 

 valde iridescent e. 



Shell smooth, subtriansrular, rather compressed, inequilateral, dark-brown; valves rather thick; beaks some- 

 what prominent; cardinal teeth large; lateral teeth nearly straight; nacre purple and very iridescent. 



I lab. West Florida, Major Le Conte. 



My cabinet and cabinets of Major Le Conte and Prof. Ilaldeman. 

 Diam. .7. Length 1.2, Breadth 1.7 inches. 



Shell smooth, subtriangular, rather compressed, inequilateral, subangular behind and 

 rounded before, subangular on the umbonial slope, dark-brown ; beaks somewhat promi- 

 nent and placed near the anterior margin; ligament very short and rather thin ; epider- 

 mis dark-brown, with indistinct, rather distant lines of growth, smooth on the superior 

 portion, striate and rather rough towards the margin, apparently without rays; cardinal 

 teeth large, rather erect, double in both valves; lateral teeth rather short, thin, and very 

 slightly curved; anterior cicatrices distinct; posterior cicatrices distinct; dorsal cicatrices 

 placed on the inferior portion of the cardinal teeth, within the cavity of the beaks; cavity 

 of the shell rather shallow; cavity of the beaks deep and angular; nacre purple, some- 

 what clouded, and very iridescent. 



Remarks. — A single specimen of this species was sent to me by Major Le Conte. The 

 beaks, being eroded, do not present the means of ascertaining if this be undulate at the 

 tip. The general outline approaches very closely to U. rubiginosus, (Nobis,) but it is 

 rather more carinatc on the posterior slope, and more compressed on the anterior portion 

 of the shell. It difl'ers entirely from that species in its nacre, belonging, in regard to 

 colour, to the complanalus group, which varies so much in purple, white and salmon. The 

 spt cimens before me are not of a deep purple, but rather pale, and clouded with white. 

 The margin and teeth are the darkest. In other individuals the colour may be found to 

 vary from dark-purple to white.* 



Prof. Haldeman's specimen is less triangular. It also came from Major Le Conte. 



Unio Oregonensis. PI. XXII. Fig. 33. 



Testu Iwvi, elliplicd, subinflalA, subinsequilalerali, poslice obtuse angulatd : valvulis crassis ,• natibus sub- 

 prominentibus ; epidermide tenebroso-olivaced, rugosd, valde slriald, obsolete radiatd; dentibus cardinalibus 

 magnis, obliquis, romprm'i* <t valde crenulatd; lateralibus longis, subcrassis curvalisque; margaritd albd tt 

 iridescente. 



* Since the above was written, I have seen, in Mr. Wheatley's collection, two specimens from New Oil 

 both of which are while, 



