SOMATOaYRUS. 61 



Ohio River and tributary streams ; Wiscon- 

 sin. 



This species is larger, and the spire is more 

 conical and sutures more deeply impressed 

 than in the altilis. The whorls are more con- 

 vex, and the umbilicus visible, although 

 narrow. 



Melania isogona, Say, is the same species, 

 and Paludma ]paUida, Lea (my figure 11) is 

 the young. 



3. SOxMATOGYRUS DEPRESSUS, Tryon. 

 Plate 17, fig. 12. 



Shell orbicular, sub-hyaline ; whorls four, 

 convex, the last large, equaling five-sixths the 

 length of the entire shell ; umbilicus narrow ; 

 aperture semicircular, labrum appressed with- 

 in ; suture impressed. 



Alt. and diam. 4 mill. 



Mississippi River at Davenport, Iowa. 



Differs from S. suhglobosus in being smaller, 

 and in the narrower aperture, of which the 

 (42) 



