﻿UNITED STATES, 93 



beaks are coarser. The young have beautiful dark green rays over the whole disk, but 

 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 character is sometimes observed in nasutus. 



Unio maconensis. PL 20, fig. 73. 



Testa laevi, valde transversa, subcompressa, ad latere planulata, valde inasquilaterali, postice subbiangulata ; 

 valvulis subtenuibus; natibus prorninulis; epidermide tenebroso-fusca, obsolete radiata; dentibus 

 cardinalibus parviusculis ; compressis, triangularis, crenulatis, in utroque valvulo duplicibus ; lateralibus 

 prselongis, lamellatis rectisque ; margarita purpurescente et iridescente. 



Shell smooth, transverse, rather compressed, subbiangular behind, very 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. 



Hab. — Flint River, near Macon, Georgia. J. C. Plant. 



My cabinet and cabinet of Mr. Plant. 

 Diam. '8, 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 centre 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. — Branchial uterus not charged, but ova were found in the ova- 

 rium. Branchial 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 filament. 

 Palpi 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 papillae on the inner 

 edges. Anal opening large, with numerous very small dark brown papillae on the 

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

 distance below.* Color of the mass a light salmon tint. 



*Two individuals have their edges united also in the middle. 



24 



