236 
cardinalibus parvis; lateralibus vix cernendis; margarita alba. 
D. 1, long. 1,4, lat. 2,7". Ten. — U. glaber t. elliptica, trans- 
versa, compressa, glabra, inaequilaterali; valvulis tenuibus; natibus 
snubprominulis, undulatis; epidermide lutea, radiata; dentibus car- 
dinalibus parvis, elevatis; lateralibus longis; margarita alba. D.0,5, 
long. 0,8, lat. 0,5“ Holston River. Ten. — U, gibber t. trian- 
gulata, compressa, inaequilaterali, postice subbiangulata}; valvulis 
subcrassis; natibus prominulis; epidermide tenebroso-fusca, den- 
tibus cardinalibus parvis; lateralibus declivibus, margarita salmo- 
nis colore tincta. Diam. 0,7, long. 1, lat. 4,8. Carryfork River. 
Ten. — U. Fanuxemensis t. elliptica, compressa, transversa, 
inaequilaterali; valvulis erassis; natibus subprominulis; epidermide 
tenebroso-fusca: dentibus cardinalibus magnis; lateralibus longis 
subcurvisque; margarita salmonis colore tincta -et iridescente. 
Diam. 0,7, long. 1,2, lat. 1,9“ Cumberland River. Ten. — U. car- 
bonarius t. subtriangulata, tumida, transversa, inaequilaterali, 
subemarginata; valvulis crassis; nalibus subprominulis; epider- 
“ide nigra; dentibus cardinalibus grandiusculis; lateralibus parvis 
subeurvisque; margarila purpurea et iridescente. D. 1,4, long. 1,4, 
lat. 2,4". Mexico. — U. folliculatus t. angusto-elliptica, trans- 
versissima, valde inaequilatera, postice subbiangulata; antice ro- 
tandata; ad latera planulata; valvulis subtenuibus; natibus vix 
prominulis; epidermide tenebroso-fusca; dentibus cardinalibus 
yarvis; lateralibus longis subeurvisque; margarita purpurea et 
iridescente. Diam. 0,5, long. 0,8, lat. 2,4“ Savannah ‚River. — 
U. medellinus t. elliptica, transversa, subcompressa inaequilate- 
rali; valvulis subtenuibus; natibus subprominulis; epidermide lu- 
teola, radiata; dentibus cardinalibus parvis; lateralibus longis sub- 
curvisque; margarila alba et iridescente, Diam, 0,7, long. 1,3, 
lat. 2,3“. River Medellin, bei Vera Cruz. — U. Lecontianus 
t. elliptica transversa, inaequilaterali, subinflata; valvulis crassis; » 
dentibus cardinalibus parvis; lateralibus longis, a cardinalibus 
separalis; margarita salmonis colore tincta. Diam. 1,2, Hi 47, 
lat. 2,8%. Georgia. — U. Muhlfeldianus t. elliptica, subcom- 
pressa, transversa, inaequilaterali; valvulis suberassis; natibus sub- 
prominulis, undulatis; epidermide luteola radiata, dentibus cardi- 
nalibus subparvis erectisque; lateralibus longis reclisque; marga- 
rita alba et iridescente. Diam. 0,8, long. 1,3, lat. 2,3“. Cumber- 
land River. Ten. — U. spinosus t. spinosa, subtriangulari, in- 
flata, inaequilaterali, postice acuto-angulata; valvulis suberassibus; 
clivo umbonali carinato; natibus vix prominentibus: epidermide 
atro-fusca, glabra; dentibus kardiatlihut deorsum inclinantibus; 
lateralibus subgrandibus subeurvisque; margarita purpurea. D. 1,2, 
long. 1,5, lat. 3,3. Altamaha, Hopeton, bei Darien, Geo. — U. pli- 
ciferus t. elliptica, inaequilaterali, subinflata, postice undulata; 
valvulis antice crassioribus; natibus prominulis; epidermide atro- 
viridi; dentibus cardinalibus submagnis; lateralibus rectis; marga- 
rita purpurea. Diam. 0,8, long. 1,2, lat. 2,1“. Mexico. — U. Tap- 
panianus t. obovata, subinflata, inaequilaterali, postice dilatata; 
valyulis tenuibus; natibus subprominentibus undulatisque; epider- 
mide fulvo-fusca; dentibus cardinalibus compressis.curvisque; la- 
