SUBTERRANEAN AMPHIPOD STYGONECTES 79 



a cave in Barry Co., Mo., all along the northwestern periphery of the 

 range, varied even further in the absence of gUls as follows: males 

 lacked sternal gills on the first pleonite and coxal gills on the seventh 

 pereopod; females lacked only coxal gills on the seventh pereopod. 

 The number of apical spines on the uropod 3 was almost invariably 

 constant with the exception of a single male from Bergman Cave, 

 Izard Co., Ark., which had three instead of two such spines. 



The most obvious quantitative variation occurred in the ratio of 

 length of antenna 1 to standard body length, and w^as more extreme 

 in males than in females, A number of measurements on samples from 

 different parts of the range indicated that there is often as much vari- 

 ation between individuals in the same population as between individ- 

 uals in different populations. With the possible exception of males 

 from extreme southeastern populations, however, where antenna 1 

 appeared to be proportionately a little longer, there seemed to be 

 little geographic pattern to this variation. Although the possibility 

 of east-west clinal variation in this character cannot be rided out, 

 with the mostly small and spotty collections that are presently avail- 

 able, an attempt to demonstrate this phenomenon would be extremely 

 difficult if not impossible. 



Type locality. — A well located 1 mile east of the Post Office 

 in Auburn, Lee Co., Ala. According to Hubricht (1943) this well is 

 (or at least was) located on the dairy farm of L. B. Yarbrough. This 

 site is further significant in that it is the type locality for a subterra- 

 nean isopod, -AsgZZws atoftameTi.sis (Stafford) (cf., Steeves, 1964). The 

 type locality is located just south of the boundary between the Ap- 

 palachian Piedmont and the Eastern Gulf Coastal Plain, and appears 

 to be situated in Cretaceous sediments (sand, gravel, and clay) of the 

 Tuscaloosa FoiTuation. Although neither Stout (1911) nor Hubricht 

 (1943) gave any figures on the depth of this well, Stout did mention 

 a stream at the bottom, and from her discussion it is assumed that 

 the well is rather shallow. 



Distribution and ecology. — The range of S. alabamensis is more 

 than twice as extensive as any other species in the genus. S. ala- 

 bamensis s. str. ranges westward from Lee Co., Ala., to Lauderdale 

 Co., Miss., north-northwestward to Tipton Co., Tenn., and then west- 

 ward across Arkansas to Latimer and Mayes Co., Okla., and north- 

 ward to Pulaski Co., Mo. The range of S. a. occidentalis is given 

 below. A major disjunction occurs in the range between Lauderdale 

 County and Tipton County and to a lesser extent between the latter 

 and Jackson Co., Ark. Presumably these large gaps represent lack 

 of collecting rather than absence of populations. Throughout most 

 of its range, S. a. alabamensis appears to inhabit shallow ground waters 

 of the upper zone of sedimentary rock and overlying mantle deposits. 



