FAMILY UNIONID.E ANODON. 203 



Color. Epidermis greenish yellow in the adults ; green in the young, which are also very 

 faintly rayed : within silvery or salmon-colored ; in some specimens, reddish. 



Vertical axis, 2'0; transverse ditto, 4"0. Diameter, 1*0. 



This shell appears to be common in various parts of this State and the adjoining States. 

 If it be, as Dr. Gould suggests, the A. newtoniensis of Lea, it has a wide southern range. 

 Say remarks, on implicata, that it is more cylindrically convex than any he ever met with. 



Anodon fluviatilis. 



PLATE XVIII. FIG. 234. 



Mylitus fluviatilis. Dillwyn, Catalogue, Vol. I. 



Anodonta cataracta. Say, Nich. Ency. Vol. 4, pi. 3, fig. 4. Russel, Essex Jour. Vol. 1, p. 60. 



Anodonta fluviatilis. Lea, Trans. Am. Phil. Soc. Vol. 6, p. 138. 



A. cataracta. Adams, Am. Jour. Sciences, Vol. 40, p. 276. 



A. fluviatilis. Gould, Invertebrata of Mass. p. 117, fig. 80. 



Description. Shell thin, fragile, inequilateral, oblong, inflated ; its greatest vertical axis is 

 from the posterior end of the ligament. Beaks at the anterior third of the shell, prominent, 

 swelling, often undulated at the tip. Basal margin slightly gaping : an indistinct ridge 

 or double fold extends from the beaks to the posterior margin. The hinge-margin, at its pos- 

 terior portion, compressed, and raised into a thin crest. Surface with concentric striae, which 

 become almost scaly folds behind. 



Color. Epidermis light green or olive, with a few short indistinct radiations ; beaks horn- 

 color : interior bluish white, iridescent. 



Vertical axis, 2 - 5 ; transverse ditto, 4*5. Diameter, 1*5. 



This species is common in almost all our mill-ponds and sluggish streams. 



Anodon pavonia. 



PLATE XL. FIG. 358. 

 (STATE COLLECTION.) 

 Anodonta pavonia. Lea, Tr. Am. Phil. Soc. Vol. 6, p. 21, fig. 65. 



Description. Shell moderately thin, inflated, transversely oblong, regularly rounded in 

 front, subacutely rounded behind : umbones large. Beak distinct, flattened above, undulated, 

 incurved, contiguous, with a slight pit in front ; basal margin regularly rounded. Surface 

 smooth and polished, with slight concentric furrows of growth ; within, with faint radiating 



stria?. 



Color. Light grass-green, with darker green waving radiating stria? on every part of the 

 shell ; beaks uniform olive brown : within bluish white, iridescent. 



Vertical axis, 1'8 ; transverse ditto, 3 "2. Diameter, 1'2. 



The characters of this large and beautiful species, first described and named by Mr. Lea, 

 appear to apply exactly to specimens derived from Onondaga lake, and for which I am in- 

 debted to Dr. Sartwell. 



26* 



