PLEISTOCENE EOSSILS 



125 



The shell of 

 Ligumia (fig. 359) is 

 thick, solid, much 

 longer than wide. Two 

 cardinals in the left 

 valve, one in the right. 

 Two laterals in the left 

 valve, one in the right. 

 The laterals are wide, 

 long, and have rough 

 edges. One species 

 still lives in Lake Erie 

 and other waters of the 

 state. 



Fig. 359 



Lampsilis (fig. 

 360) appears twice in the key as some 

 of the species are elongated and others 

 are almost circular in outline. The 

 shell may be as much as 6 inches or 

 more long; it has one or two cardinals 

 and one lateral in the right valve; two 

 cardinals and two laterals in the left 

 valve; female shells are strongly 

 swollen behind. The genus contains 

 many species, some of which are still 

 living in the rivers and lakes of Ohio. 

 They are often numerous in Pleisto- 

 cene deposits. 



In Leptodea (fig. 361) the shell 

 is very thin and fragile, straw-yellow, 



prolonged into a wing posteriorly. Two cardinals in the left valve, one in the right. Two 

 laterals in each valve. It may be distinguished from the next genus by the greater development 

 of the cardinal teeth and the thinness of the shell. 



Fig. 361 



Proptera (fig. 362) has a 

 large shell with a wing which is 

 similar to that of Leptodea . It is 

 distinguished from that genus by 

 the imperfectly developed cardina' 

 teeth. Living shells are dark 

 brown on the outside of the shell, 

 various shades of purple inside, 

 and the color is often preserved 

 in fossil shells. 



