SUBTERRANEAN AMPHIPOD STYGONECTES 



145 



The pizzinii group. — The mutually exclusive ranges of the two species 

 of the pizzinii group are shown in figure 34. Distributional data indi- 

 cate a rather wide range for S. pizzini s. str., extending from the 

 eastern margin of the Piedmont (Fall Zone) in the vicinity of Wash- 

 ington, D.C., and Fairfax Co., Va., northeastward through Maryland 

 and into Pennsylvania. The range of this species is apparently re- 

 stricted to the Piedmont province. S. indentatus, on the other hand, 



Figure 34. — Distribution of Slygonedes in eastern United States. [The tenuis group: 

 X S. allegheniensis; + S. hayi; 9 S. t. tenuis. S. t. potomacus: O single localities, 

 three or more nearby localities. The pizzinii group: A S. indentatus; A'^S. pizzinii. 

 ? possible hybrid population between S. hayi and S. t. potomacus (see text). Two 

 symbols in a circle indicate two species from the same locality.] 



