14 Trans. Acad. Sci. of St. Louis. 



striate, that of the retractor pedis muscle deep, pit-like, some- 

 times confluent with that of the adductor ; cavity of the beaks 

 shallow, with a row of minute pit-like dorsal cicatrices some 

 distance within the margin of the plate; nacre rich purple, 

 light, iridescent, the latter feature especially marked pos- 

 teriorly. 



Animal not observed. 



Length, 111.25 mm. ; breadth, 40.00 mm; height, 69.00mm. 



In very good specimens, not too old, small and well marked 

 foldings, disposed at an angle with the umbonal angle and 

 increasing in number towards the umbones, may be noticed. 

 These are characteristic, and serve to indicate the possible 

 aflinities of this species and ZT^iio incrassatus Lea, from the 

 Chattahoochee, Oostanaula, and other Georgia streams. 



The ligure given herewith is drawn from a fine specimen ob- 

 tained in the Cumberland river, Tennessee, at Nashville, where 

 the form is very abundant. Larger but less perfect speci- 

 mens are common. In nearly all the great rivers of the south, 

 west of the Appalachian system, this form occurs and usually 

 in great abundance. It has not yet been obtained west of the 

 Mississippi, so far as present information extends. 



Unio cuneus Conrad. 



Monograph of Unio, PI. LVIII, Fig. 1, 1836. 



Four specimens were found in the Saline river, at Benton. 

 The species was described from the Little Red river, Arkan- 

 sas, by T. A. Conrad. It has long been properly regarded 

 as identical with Unio coccineus Hildreth and should no longer 

 be distributed under its Conradian name. Doctor Ward, of 

 Ohio, many years ago distributed the white-nacred variety of 

 this form under the manuscript name of Unio gouldianus 

 Ward, but never described it. The name was adopted by Dr. 

 John Jay, of New York, and published by him in his " Cata- 

 logue of Shells in the Jay collection." 



The typical forms have a warm pink nacre but are not so 

 common as the white-nacred variety. The range of the 

 species is from western New York to North Alabama and 

 west to central Kansas. In the rivers of Iowa it is both 

 abundant and fine. 



