UXITKD STATES. 93 



beaks are coarser. The 3'oung have beautiful (hirk green rays over tlie whole disk, Ijnt 

 they disappear on approach to adolescence, and the whole surface becomes very dark. 

 On the posterior slope of the young shell the rays are capillary and very distinctly 

 marked. On the sides of some of the adult specimens there are a few nearly parallel 

 perpendicular indistinct folds, which (sharacter is sometimes observed in na-snlufi. 



Unio maconensis. pi. 20, fig. 7o. 



Testil la;vi, valde trausvcrsn, subcninprossil, ad latere planulatu, valdo inajfjuilateralij postice subbiangulata ; 

 valvulis subtcnuibus; natibu.s prominulis; epidermide teiiebrcso-fusca, ob.soletu radiata; dentibus 

 cardinalibus parviusculis ; compressis, triangularis, crcnulatis, in utroque valvule duplicibus ; lat«ralibus 

 pndongis, laiuellati.s rectisquc ; niargarita purpurescente et iridcscente. 

 Shell smooth, transverse, rather compressed, subbiangular behind, verj- inequi- 

 lateral ; valves rather thin ; beaks slightly prominent; epidermis dark brown, striate ; 

 cardinal teeth rather small, compressed, triangular, crenulate double in both valves ; 

 lateral teeth very long, lamellar and nearly straight ; nacre purple and iridescent. 

 Proc. Acad. Nat. Sci. 1857, p. 172. 

 Hah. — Flint Eiver, near Macon, Georgia. J. C. Plniit. 

 My cabinet and cabinet of Mr. Plant. 

 Diam. "S, Length 1-5, Breadth 3-3 inches. 



Shell smooth, transverse, rather compressed, flattened at the side, very inequila- 

 teral, subbiangular behind, obliquely rounded before ; substance of the shell rather 

 thin ; beaks slightly prominent ; ligament long and thin ; epidermis dark brown, striate, 

 without rays ; umbonial slope raised into a well defined angle; cardinal teeth rather 

 small, compressed, triangular, crenulate, oblique and double in both valves ; lateral 

 teeth very long, lamellar and nearly straight ; anterior cicatrices distinct and moder- 

 ately impressed ; posterior cicatrices confluent, scarcely perceptible ; dorsal cicatrices 

 small and placed in the c^entre of the cavity of the beaks ; cavity of the shell rather 

 shallow and wide; cavity of the beaks very shallow and rounded ; nacre purple and 

 iridescent. 



Soft^ Parts. — BranchioJ utenis not charged, but ova were found in the ova- 

 rium. Branekia? very wide, thin, slightly curved below, posteriorly very oblique, 

 inner ones somewhat the larger, free more than half the length of abdominal sack. The 

 posterior ends do not reach the edge of the mantle, but are attached to it by a fdament. 

 Rilpi rather large, rounded below, angular behind, united about one-third down the 

 posterior edges. Mantle thin, slightly thickened at the margin, which is broad. 

 Branchial opening rather small, with numerous small brown papilla^ on the inner 

 edges. Anal openimj large, with numerous very small dark brown papilkv on the 

 inner edges. Super-anal openinr/ long, slightly colored on inner edges, united for some 

 distance l)elow.* Color of the mai^s a light salmon tint. 



*'l'w.> iiulivi.liial!' hitvc (licii- .-.lii.-s unitp.l al.-^.. in llic lui.l.ll.- 

 24 



