FRESH WATER AND LAND SHELLS. SL 
A single specimen only is under my inspection, and this is much eroded on the superior 
portion, leaving only false beaks. It is not, of course, possible to say whether the tips 
are undulate or not. 
Unio succissus. Pl]. XXI. Fig. 32. 
Testa levi, subtriangulari, subcompressa, inxquilaterali, tenebroso-fuscd; valvulis subcrassis; natibus 
subprominentibus ; dentibus cardinalibus magnis; lateralibus parvis subrectisque; margarita purpurea et 
valde iridescente. 
Shell smooth, subtriangular, rather compressed, inequilateral, dark-brown; valves rather thick; beaks some- 
what prominent; cardinal teeth large; lateral teeth nearly straight; nacre purple and very iridescent. 
Hab. West Florida, Major Le Conte. 
My cabinet and cabinets of Major Le Conte and Prof. Haldeman. 
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 carinate on the posterior slope, and more compressed on the anterior portion 
of the shell. It differs entirely from that species in its nacre, belonging, in regard to 
colour, to the complanatus group, which varies so much in purple, white and salmon. The 
specimens 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. 
Umio Orrconensis. Pl. XXII. Fig. 33. 
Testa lxvi, ellipticd, subinflata, subinequilaterali, posticé obtuse angulata; valvulis crassis; natibus sub- 
prominentibus; epidermide tenebroso-olivaced, rugosa, valde striata, obsoleté radiatd; dentibus cardinalibus 
magnis, obliquis, compressis et valdé crenulata; lateralibus longis, subcrassis curvatisque; margarilé alba et 
iridescente. 
* Since the above was written, I have seen, in Mr, Wheatley’s collection, two specimens from New Orleans, 
both of which are white. 
