SUBTERRANEAN AMPHIPOD STYGONECTES 69 



with 21 to 29 segments. Antenna 2 with 9 to 12 flagellar segments. 

 Propod palmar margins of gnathopods straight to slightly convex. 

 Uropod 1: rami together with up to 25 spines, peduncle with about 

 18 spines. Telson less tapered distally; armed with 14 to 18 unequal, 

 apical spines, none of which are deflected or tined. 



Variation.' — Populations distributed along the eastern margin of 

 the Valley and Ridge Province and in the western part of the Pied- 

 mont Upland in the vicinity of Lancaster Co., Pa., appear to vary 

 slightly from populations elsewhere within the range. In eastern 

 populations palmar margin concavity is slightly more pronounced, 

 appendages more slender, body size somewhat reduced, and in some 

 males sternal giUs are absent on pleonite 1. In general, however, 

 differences are subtle and on the basis of material collected to date, 

 reliable taxonomic differences could not be dehneated. 



The size relationship of antenna 1 and 2 to each other and to stand- 

 ard body length in males is shown by the regression line in figure 16. 

 Unhke the cosely related S. tenuis, the length of antenna 2, although 

 proportionately long, does not exceed the length of antenna 1 in larger 

 males of this species. By comparing the graph in figure 16 with that 

 in figure 14, a significant quantitative difference between S. tenuis 

 and S. allegheniensis in allometric size relationship of antenna 1 and 

 2 becomes apparent. 



Type locality. — ^A spring at Ilion, Herkimer Co., N.Y. 



Distribution and ecology. — S. allegheniensis occm's in sub- 

 terranean waters of the Appalachian Plateau in south-central New 

 York, in the Allegheny Mountain section of the Appalachian Plateau 

 of west-central Pennsylvania and western Maryland, and in the Valley 

 and Ridge Province of central Pennsylvania. In the east, as already 

 noted, the range extends into the Piedmont Upland in the vicinity 

 of Lancaster Co., Pa. Two sizeable disjunctions occur in the pres- 

 ently known range: an 80 mile gap between Centre Co., Pa., and 

 Chemung Co., N.Y., and a 50 mile gap between Mifflin and Lebanon 

 Counties, Pa. 



This species is associated almost exclusively with subterranean habi- 

 tats developed in Paleozoic, sedimentary bedrock. In western and 

 central Pennsylvania and in the Albany, Schoharie County area of 

 east-central New York this species is known only from cave waters. 

 In central New York records are from wells and springs occurring in 

 lower Paleozoic sandstones and limestones (but mostly Devonian 

 sandstones). Marginal populations in eastern Pennsylvania are 

 known mostly from seeps and springs developed in lower Paleozoic 

 sandstones and limestones. In caves, S. allegheniensis is usually 

 found under rocks in small streams or in shallow pools with silt 

 bottoms. In John Friends Cave this species has been collected on two 



