UNITED STATES. 10 



cartlinalibus parvis, pvramidati.s crcnulatisquc ; latcralibus sublongis, laniellatis subfurvisiiuc ; uiar- 

 irarita vol purpurea vol salmonis colore tincta et iridescente. 



Shell smooth, oblong, rather inflated, flattened at the side, ina)quilateral ; valves 

 rather thin, thicker before ; beaks a little prominent, undulate at the tips ; epidermis 

 blackish, shining and obscurely rayed; cardinal teeth small, pyramidal and crenulate ; 

 lateral teeth rather long, lamellar and somewhat curved; nacre either purple or 

 salmon color and iridescent. 



Proe. Acad. Nat. Sci., 1857, p. 171. 



Ilah. — Streams near Columbus, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. -5, Length 8, Breadth lu inches. 



Shell smooth, oblong, rather inflated, flattened at the sides, inequilateral, rounded 

 behind; substance of the shell rather thin, a little thicker before; beaks a little 

 prominent, finely undulate at the tips; ligament short, somewhat thick and light 

 brown ; epidermis blackish, shining, obscurely rayed and with rather distant marks 

 of growth ; umbonial sloiDe raised and much rounded: cardinal teeth small, pyramidal, 

 crenulate, compressed and double in both valves ; lateral teeth rather long, lamellar 

 and somewhat curved ; anterior cicatrices distinct ; posterior cicatrices confluent ; 

 dorsal cicatrices placed under the plate immediately behind the cardinal tooth ; 

 cavity of the shell rather deep and wide ; cavity of the beaks rather shallow and 

 subangular ; nacre purple and salmon color. 



Soft parts. — Branchial uterus not charged, but ova were found in the ovarium. 

 liranchiai free nearly the whole length of abdominal sack, large, rounded below, 

 inner one much the larger. Palpi rather small, subangular, united above on the 

 posterior edges. Mantle thickened and double on the posterior margin, colored at the 

 siphonal openings and truncate behind. Branchial opening very large, with numerous 

 small brown papillaj on the inner edges. Anal opening large, with very minute, 

 brown papilla; on the inner edges. Super-anal opening rather small, colored within 

 and slightly united below. Color of the mass dirty white. 



Remarks. — This little, very dark brown or blackish species, is very nearly allied 

 to nigcllns (nobis). It is rather more transverse, not quite so high on the umbonial 

 slo{)e, nor has it so smooth, dark and polished, an ejiidermis. One of the youngest 

 specimens is perfect at the beaks and displaj-s a number of irregular undulations 

 very much like those of complanatus. This young one is light brown and has well 

 marked rays on the posterior half, while the adults have very obscure ones or none. 



Unio radiAx\s. pi. 23, fig. 8-1. 



Testa lavi, clliptica, subinflata, inacquilatcrali, postice rotundati ; valvulis subtenuibus, antice crastfioribu.s, 

 natibus proiuinulis, ad apices undulatis ; epidermido lutei, politu, valdc radiata; deutibus cardinalibus 

 gubgrandibus, crectis, subconicis crcnulatisquc ; latcralibus sublongis, lamcUatis subrcctisque ; mar- 

 garita vel alba vel rosaceil et valdO iridescente. 



