SUBTERRANEAN AMPHIPOD STYGONECTES 39 



subacute; ventral margins of plates 1-3 with 1,1, and 2 spines, re- 

 spectively. Pleopod 1, inner ramus up to 30 percent longer than 

 peduncle. Uropod 1 with up to 43 spines; outer ramus about 80 

 percent as long as inner ramus, about 60 percent as long as peduncle. 

 Uropod 2 with up to 27 spines; outer ramus about 2/3 the length of 

 inner ramus, which is about equal to peduncle in length. Uropod 3: 

 peduncle armed with 1 or 2 distolateral spines; ramus very small, 

 only about 1/5 as long as peduncle and armed with 1 long spine 

 apically. Telson about 40 percent longer than broad, broader 

 proximaUy than distally; armed with 12 to 16 dorsolateral spines in 

 both sexes and apically with about 10 spines in female and about 13 

 spines in male. 



Variation. — Preliminary measurements give strong evidence for 

 a rather pronounced positive allometric increase in length of pereopod 

 7 and antenna 1 in relation to overall increase in body length as 

 indicated by the data given in table 3. Measurements on a number 



Table 3. — Appendage to body length ratios in females of Stygonectes gracilipes 



of females (selected because of the much greater abundance of this 

 sex in available samples), ranging in size from 9.00 to 12.50 mm, 

 indicate up to a 10 percent increase in pereopod 7 to body length 

 ratio. Of further significance is the fact that 18.00 mm females 

 from Dam Number 4 Cave were generally similar to the 12.50 mm 

 female from Skyline Caverns in regard to the indicated ratios, thus 

 implying the possible existence of different growth rates in these 

 two populations. But since smaller females were not available 

 from Dam Number 4 Cave, the approximate size at which sexual 

 maturity might be reached in this population could not be deter- 

 mined. In Skyline Caverns samples, however, marginally setose 

 brood plates were first noted on females between 10.00 and 11.00 mm 

 in length, and none of the female specimens were longer than 12.50 mm. 

 Type locality. — Skyline Caverns, Warren Co., Va. The type 

 series was collected from several small pools and streams. Skyline 



