115 



*outh Tennessee and in the Black Warrior River of Alabama. The heaviest, 

 largest and glans like forms from the south occur in the Coosa River, a tributary 

 to the Alabama, just above Wetumpka. Similar shells were taken in numbers in 

 the Cahaba River, in Bibb County, also tributary to the Alabama. 



UnIO AMGDAIAM Lea. 



Observations on the Genus Unio. Vol. IV, p. 33, pi. XXXIX, tig. 1, 1843, 



from Lake George. Florida ; Tran.s. Am. Phil. Soc, 2d Ser., Vol. IX, pi. 39, fig. 



1, pp. 275. 27H. See also Simpson, " Xotes on Florida Unionida?, "' Proc. U. S. 



Nat. Mus. Vol. XV. pi. LXVII. fig. 3. p. 42(i, 1892. 



I'nio paj>yniceiis (4ould. Proc. Bost. Soc. Xat. Hist., Vol. II. p. 53, 1845. 



Florida. Latin diagnosis ; no figure. 



The following description of Unio aiwidahnn is based upon excellent speci- 

 mens from the original locality. 



Shell small, striate, somewhat intlated, nearly oval in outline, rounded be- 

 fore, subangular i)osteriorly, viewed dorsally the outline is rounded cuneate pos- 

 terior to the umbones, female slightly emarginate on the ventral border; 

 epidermis striate, light straw colored over the disk, greenish to greenish-yellow 

 near" the ventral margin, faintly rayed on the posterior dorsal slope in the manner 

 characteristic of all the parvus group; ligament short, thin, light horn-colored; 

 lines of growth distinct, broad, and much darlier than the balance of the disk; 

 anterior or cardinal teeth double in the left and single in the right valve, though 

 an occasional specimen exhibits a tendency to double teeth in both valves, flat- 

 tened, plate-like, crenate; posterior teeth double in the left and single in the 

 right valve, long, lamellar, straight, striate, particularly toward the extremities; 

 anterior cicatrices distinct, the adductor rather deeper or impressed, that of the 

 protractor pedis rather large, oval, but slightly impressed; posterior cicatrices con- 

 riuent, scarcely impressed, very iridescent ; cavity of the beaks rounded and shal- 

 low, with a row of pit-like and minute cicatrices just under the dorsal plate; 

 nacre white, pinkish or salmon tinged towards the cavity of the beaks, beautifully 

 iridescent over the entire posterior half, but the play of iris-like colors is most 

 marked on the posterior margin beyond the j)allial cicatrix, which is very faintly 

 impressed. 



The average dimensions are: Length, 3.1 mm.; width. 1.22 mm.; heighth, 

 1.82 mm. 



Some specimens of this shell approach the form of Unio minor Lea in that the 

 cardinals are much heavier than usual and the substance of the shell is much 

 thicker; in these forms also the posterior teeth are incrassate. The tout engi'mbl'' 



