OF THE MOLLUSCA OF IOWA. 67 



and some portions of eastern Iowa. Also fossil in the 

 loss. 



8trohila labyrinthica Say. A minute species very gen- 

 erally distributed and in suitable places occurring quite 

 abundantly. 



Stenotrema hirsulum Say. Rather common in many lo- 

 calities ; rare in others. When this species occurs abun- 

 dantly its congener, /S. mo?iocZo/i, appears to be rare, and 

 vice versa. 



Stenotrema monodon Rackett. Generally distributed, 

 but only locally common. The variety leai is also common 

 in Scott, Johnson and contiguous counties. This species 

 occurs quite abundantly in the loss ; as has been referred 

 to by McGee and Call {loc. cit.) the loss forms of this spe- 

 cies "present some important differential characters ; the 

 apices being more elevated, the whorls more convex, and 

 somewhat loosely coiled with the apertures more lunate 

 than in recent specimens. The reflected portions of the 

 lip and the parietal teeth are also less calcareous ; in all 

 other respects they correspond generally with the variety 

 of the recent form known as S. monodon var. leai." 



Tridopsis palliata Say. Bonaparte, Ft. Madison, Bur- 

 lington : not common. Until very recently, this species 

 was unknown in Iowa. 



Tridopsis appressa Say. This species has recently been 

 collected at Burlington ; but it is quite rare. 



Mesodon albolahris Say. This species appears to be of 

 very rare occurrence in eastern Iowa ; but in the central 

 portion of the state it is one of the most abundant land 

 forms ; and especially is it common in the vicinity of Des 

 Moines, where on warm rainy days in the woodland cover- 

 ing the bhifls it is found in great profusion feeding upon 

 mushrooms ; a dozen or more snails often being collected 

 about a single tuft of these plants. 



