SCAMMON : THB UNIONID^ OF KANSAS, PART I. 295 



Hal line impressed the anterior half. Dorsal cicatrices a long, 

 narrow pit on the inner surface of the interdentum, often 

 with auxiliary pits in the cavity of the umbones. Nacre 

 variable, white, salmon-pink, rarely purple. 



L. recta is present all over the Mississippi, the Alabama 

 and the St. Lawrence drainage systems. It is also found in 

 Michigan and the Red River of the North. In Kansas its 

 distribution is peculiar. In the rivers of the southern area it 

 is abundant, and it is also common in the Marais des Cygnes 

 system. In the Kansas system, however, it is confined to 

 the western tributaries ; only one specimen has been re- 

 ported from below Mill creek, in Wabaunsee county, about 

 120 miles from the juncture of the Kansas with the Missouri 

 river. The one specimen was a fine male and was found in 

 the Wakarusa river, near Lawrence. Above Mill creek the 

 species is fairly common. This peculiar distribution will be 

 discussed in a later paper. Recta is not choice of its loca- 

 tion, being found either in deep or shallow water and in a 

 gravel or mud bottom. 



L. recta is not a variable species, aside from the decided 

 irregularity in the color of the nacre. The shining black 

 epidermis will distinguish it at once from L. anodontoides 

 and L. fallaciosa, to which it is very closely related. It is a 

 lighter shell than Unio gibbosus, which it somewhat resem- 

 bles in form, and its beak sculpture is entirely different, that 

 of recta being made up of fine and numerous loops, while 

 the ridges of gibbosus are few and coarse. 



Lampsilis subrostrata Say. Plate LXVII, figs. 1, 2. 

 Unio subrostratus Say, New Harm. Diss. , Jan. 15, 1831. 

 Unio topekaensis Lea, Proc. Acad. Nat. Sci. Phila., xn, 1868, p. 144. 



Shell rather small, long ellipsoid, rather thin, females 

 slightly swollen, males somewhat compressed. Anterior mar- 



* Not accurate : a broken shell. 



