100 



U.S. NATIONAL MUSEUM BULLETIN 259 



Table 5. — Variation in the ratio of length of 1st antenna to length of body in different 

 populations of Stygonectes russelli, new species 



Minor variation was noted in abdominal side plates, uropods 1 and 2, 

 and the telson. Quantitative variation in the ratio of length of first 

 antenna to length of body is shown in table 5. The data compiled 

 in this table was taken from populations with sample sizes of five or 

 more; sexes were lumped and measurements were not made on speci- 

 mens which appeared to be sexually immature. 



Type locality. — Tippits Cave, about 5 miles north of Killeen, 

 Coryell Co., Tex. The type locality is located on the Fort Hood 

 Military Reservation. The type series was collected from a small 

 pool containing blue-green algae and troglobitic isopods, Asellus 

 species (J. Reddell, in litt.). 



Distribution and ecology. — As presently delimited, the range 

 of this species covers most of the eastern half of the cavernous lime- 

 stone area of central Texas, although large gaps occur at several in- 

 tervals. In general, the range extends from western Kerr County 

 eastward to Kendall County, then northeastward through Travis 

 County to southern Corj^ell County and from there westward to San 

 Saba County and southwestward to Mason County. Continued 

 collecting will undoubtedly uncover many additional populations of 

 this species as well as resolve some of the problems concerning its 

 pronounced morphological variation. 



