\E\v unionid.t; of the united states. tyj 



short, rather thick and light brown; epidermis reddish olive, usually rayed over the 

 whole disk, with distant marks of growth; umbonial slope raised and rounded; pos- 

 terior slope wide, cordate, usually yellowish ; cardinal teeth rather large, conical, 

 crenulate, double in both valves ; lateral teeth short, thick and somewhat curved ; 

 anterior cicatrices distinct, small, deeply impressed; posterior cicatrices confluent, 

 large and well impressed ; dorsal cicatrices small, placed on the plate above the centre 

 of the cavity of the beaks ; cavity of the shell rather deep and rounded ; cavity of the 

 beaks rather deep and obtusely angular; nacre white. 



EemarLs. — This diminutive species is very near to capscc/ormis, (nobis), but is 

 thicker and much smaller. It has, usually, capillary rays over the whole disk. The 

 enlargement of the female disk is at the posterior basal margin, and more like that of 

 Stewardsonii, (nobis), than capuceformis, and it is usually lighter colored. The speci- 

 men figured is a female. The enlargement takes place after the third growth. The 

 nacre of all I have seen is white. 



Unio Meredithii. pi. 0, fig. 214. 



Testa sulcata, subtrigona, valdii compressii, postice obtusi angulata, inwquilaterali ; valvules subcrassis, an- 

 tic6 crassioribus ; natibus prominulis ; epidermide orocea ; dentibus cardinalibus subcrassis crenulatis- 

 f|ue ; lateralibus crassis, curtis subrectisque ; margarita, subcroceil at iridcscente. 



Shell sulcate, subtriangular, very much compressed, obtusely angular behind, ine- 

 quilateral; valves rather thick, thicker before; beaks slightly prominent; epidermis 

 reddish yellow; cardinal teeth rather thick and crenulate; lateral teeth thick, short 

 and nearly straight; nacre light reddish yellow and iridescent. 

 Proc. Acad. Nat. Sci. 1858, p. 40. 



Hah. — Tennessee River, Tuscumbia, Alabama. L. B. Thornton, Esq, 



My cabinet and cabinets of L. B. Thornton, Esq. and B. Pybas. 

 Diam. -7, Length 1-3, Breadth 1-8 inch. 



Shell sulcate, subtriangular, very much compressed, obtusely angular behind, ine- 

 quilateral ; substance of the shell rather thick, thicker before ; beaks slightly promi- 

 nent; ligament short, thick and light brown; epidermis reddish yellow, with distant, 

 distinct lines of growth ; umbonial slope slightly raised and rounded ; posterior slope 

 very oblique, compressed, but slightly raised, with an indistinct impres.sed line from 

 the beaks to the margin ; cardinal teeth rather thick, crenulate ; lateral teeth thick, 

 thicker towards the end, short and nearly straight ; anterior cicatrices distinct, rather 

 large and well impressed ; posterior cicatrices distinct, rather large and moderately 

 well impressed ; dorsal cicatrices placed above the centre of the cavity of the beaks ; 

 cavity of the shell shallow and wide ; cavity of the beaks shallow and rounded ; nacre 

 light reddish yellow and iridescent. 



