34 Trans. Acad. Sci. of St. Louis. 



of the retractor-pedis muscle circular, pit-like, impressed at 

 extreme end of lateral tooth ; pallial cicatrix well impressed 

 throughout, but especially marked anteriorly ; dorsal cicatrices 

 irregularly crowded and placed near the inferior edge of the 

 plate, which connects the lateral and cardinal teeth ; nacre 

 usually silvery white, occasionally salmon, or warm pink, 

 iridescent posteriorly. Length, 54.50 mm. ; breadth, 15.28 

 mm.; height, 32.76 mm. 



The original localities are the White and Current rivers of 

 Arkansas and Missouri; and Jack's Fork of the Current river, 

 Missouri. A single specimen referable to this form has been 

 seen from the Little Red river, at Clinton. 



Unio parvus Barnes. 



Am. Jour, of Sci. and Arts, 1st series, Vol. VI, 1823, 

 p. 274, Fig. 18 ; Lea figures the animal in Jour. Phila. 

 Acad. Nat. Sci., 2d series, Vol. IV, PI. XXIX, Figs. 

 102, 102a; Conrad, Monography of Unio, 1836, PL IX, 

 Fig. I; Reeve, Conchologia Iconica, Vol. XVI, Unio 

 Plate XXXV, Fig. 186, a very poor figure from a 

 specimen in the Museum Cuming. 



Unio paulus Lea. Trans. Am. Philos. Soc, Vol. 

 VIII, 1840, p. 213, PL XV, Fig. 29. From the Chatta- 

 hoochee river, Georgia. 



Unio minor Lea. Trans. Am. Philos. Soc, Vol. IX, 

 1843, p. 276, PL XXXIX, Fig. 3. From Lakes Monroe 

 and George, Florida. 



Unio marginis Lea. Jour. Acad. Nat. Sci. Phila., 2d 

 series, Vol. VI, p. 255, 1868, PL XXXI, Fig. 69. From 

 Dougherty county Georgia. 



Unio corvinus Lea. Jour. Acad. Nat. Sci. Phila., 2d 

 series, Vol. VI, 1868, p. 310, PL XLVIII, Fig. 123. 

 From Flint river, Georgia, and Neuse river, North 

 Carolina. 



Unio vesicularis Lea. Jour. Acad. Nat. Sci. Phila., 2d 



series, Vol. VIII, 1874, p. 37, PL XII, Fig. 34. From 



Lake Ocheechobee, Florida. 



The Arkansas localities for this form are the' v St. Francis 



river, at Wittsburg ; Ouachita river, at Arkadelphia; Saline 



