SUBTERRANEAN AMPHIPOD STYGONECTES 55 



angle of propod. Segment 4 of pereopod 6 and basis of pereopod 7 

 normal. Uropod 3, ramus only about 30 to 35 percent as long as 

 peduncle and armed apically with 2 large spines and 1 small spine. 

 Telson just slightly longer than broad, armed laterally with 2 spines 

 per side and apically with 10 unequal spines. 



Variation.' — Male secondary sex characters, i.e., propod palmar 

 margin notch, expanded foiu"th segment of pereopod 6, and ventrally 

 produced distal lobes of pereopod 7, did not appear to be completely 

 developed in animals less than 7.50 to 8.00 mm in length. 



Type locality.— Outlet of drain, 3 miles northwest of Suffolk, 

 Nansemond Co., Va. 



Distribution and ecology. — This species is known only from 

 two drain outlets in Nansemond Co., Va.; the two localities being 

 about seven miles apart. S. indentatus appears to be an inhabitant 

 of interstitial groimd water habitats associated with unconsolidated 

 Cenozoic sediments of the eastern Coastal Plain. The proximity 

 of this species to the Great Dismal Swamp, and its occurrence in 

 drain outlets presumably fed by superfcial subterranean seepage 

 would indicate an extremely shallow ground-water habitat. 



The smallest females with marginally setose brood plates were 

 only 6.00 mm long. The January collection contained four ovigerous 

 females, all about 7.50 mm in length and carrying 3, 4, 6, and 11 

 eggs, respectively. 



TENUIS Group 



Diagnosis." — ^Adult size range up to 19.50 mm. Males where 

 known usually larger than females. Antennae extremely variable 

 in length. Mandible well developed. Maxilla 1, inner plate with 

 4 to 7 long, plumose setae. Maxilla 2, inner plate with 2 to 8 long, 

 obhquely placed, plumose setae. MaxiUiped: inner plate with 3 

 to 6 (usually 3 or 4) thick, apical spines; outer plate reaching nearly 

 to or rarely just beyond apex of 1st palpal segment. Lower lip: 

 inner lobes distinct, varying from moderately small to rather broad. 



Gnathopod 1: propod larger than that of gnathopod 2, palmar 

 margin concave, straight, or rarely convex. Pereopod 5 onl}'" 55 to 

 60 percent as long as pereopod 7, excepting S. reddelli, S. russelli, and 

 S. bowmani, in which pereopod 5 is proportionately longer. Pereopod 

 6 longer than pereopod 5 but a little shorter than pereopod 7 with 

 the exception of S. bowmani in which 7th pereopod is notably shorter 

 than the 6th. Bases of pereopods 5-7: posterior margins nearly 

 straight to moderately convex; distoposterior lobes distinct, usually 

 rather broad. 



Abdominal side plates: posterior margins typically broadly convex; 

 posterior corners poorly developed or indistinct, sometimes incurving 



