SUBTERRANEAN AMPHIPOD STYGONECTES 89 



Gnathopod 1 : propod palmar margin deeply concave, armed with a 

 double row of about 9 spine teeth; posterior angle with 1 large spine 

 and 5 smaller spines on outside, 5 small spines on inside; posterior 

 margin with 5 sets of setae; lateral setae few in number, mostly singly 

 inserted. Gnathopod 2: propod palmar margin deeply concave, 

 armed with a double row of about 8 spine teeth; posterior angle 

 with 1 large spine and 4 smaller spines on outside, 4 small and 2 

 medium-size spines on inside; posterior margin with 5 or 6 sets of 

 setae; superior lateral setae triply, doubly, and singly inserted, 

 inferior lateral setae doubly and singly inserted. Coxal plates of 

 pereopods 2, 3, and 4 about like those of S. alabamensis but with a 

 few more marginal setae. Pereopod 7 between 45 and 50 percent as 

 long as body, a little longer than pereopod 6 and 40 to 45 percent 

 longer than pereopod 5. Bases of pereopods 6 and 7 relatively 

 narrow, about 50 percent longer than broad; basis of pereopod 5 

 somewhat broader proportionately. Dactyls of pereopods 5 about 40 

 percent as long as corresponding propod, those of pereopods 6 and 7 

 about 25 percent as long as corresponding propods. Median sternal 

 and pleonite sternal gills absent. 



Abdominal side plates corresponding to those of S. alabamensis 

 and as shown in figure 21. Pleopod 1, inner ramus about 45 percent 

 longer than peduncle. Uropod 1 : inner and outer rami about equal in 

 length, about 60 percent as long as peduncle; outer ramus armed with 

 up to 12 spines; inner ramus with up to 14 spines; peduncle with about 

 15 spines. Uropod 2: outer ramus up to 65 percent as long as inner 

 ramus which is nearly as long as peduncle, armed with 9 spines; 

 inner ramus armed with up to 12 spines; peduncle with 6 spines. 

 Uropod 3 : ramus about 25 percent as long as peduncle, armed apically 

 %vith 2 spines; peduncle with 2 or 3 small lateral spines. Telson 

 subrectangular, apically convex, about 55 percent longer than broad; 

 armed dorsolaterally with a double set of 4 spines on either side and 

 apically with 10 spines. 



Female. — Differing from the male as follows: Antenna 1 up to 

 65 percent as long as body and up to 50 percent longer than antenna 

 2; primary flagellum with 29 or 30 segments. Antenna 2, flagellum 

 with 10 segments. Gnathopod 1, propod palmar margin less concave, 

 armed with smaller and 1 or 2 fewer spine teeth. Gnathopod 2, 

 propod palmar margin less concave, armed with smaller and a few 

 less spine teeth. Uropod 1, outer ramus with a few more spines. 

 Telson not as elongate, only about 35 percent longer than broad; 

 armed dorsolaterally with a single set of 3 or 4 spines per side and 

 apically with 10 spines. 



Type locality. — Seep, 0.5 mile east of Greenville, Wayne Co., 

 Mo. The type locahty marks an exit for ground waters resurging 



