SUBTERRANEAN AMPHIPOD STYGONECTES 121 



Diagnosis. — Distinguished from S. pecki, to which it appears to be 

 rather closely allied, by proportionately shorter 1st antenna, smaller 

 spine teeth on gnathopod propods, fewer spine teeth on propod of 

 gnathopod 2, proportionately longer dactyls and broader bases of 

 pereopods 5-7, proportionately longer and more spinose outer ramus 

 of 1st ui'opod, proportionately shorter and less spinose outer ramus of 

 2nd uropod, and 1 or 2 less apical spines on ramus of 3rd m'opod. 

 Largest female, 8.25 mm.; male unknown. 



Female. — Antenna 1 about 50 percent as long as body, about 

 50 percent longer than antenna 2; primary fiagellum with up to 22 

 segments; accessory fiagellum extending about 1/2 the distance of 

 primary flagellar segment 2. Antenna 2, fiagellum with 8 segments. 

 Mandible: molar a little less prominent than in S. pecki; palpal segment 



3 with 9 or 10 long setae, segment 2 with 9 setae. Maxilla 1, inner 

 plate with 5 apical, plumose setae. Maxilla 2, inner plate with 5 

 long, obliquely placed, plumose setae. Maxiiliped, inner plate with 



4 or 5 thick, apical spines. Lower lip, inner lobes smaU. 

 Gnathopod 1 : propod palmar margin not especially oblique, straight, 



armed with a double row of 7 or 8 rather smaU spine teeth; posterioi 

 angle with 1 large spine and 3 smaller spines on outside, 4 small spines 

 on inside; posterior margin with 4 sets of setae; lateral setae few in 

 number, singly inserted. Gnathopod 2: propod about equal in size 

 to 1st but a little more slender; palmar margin generally straight, 

 armed with a double row of 7 small spine teeth; posterior angle \vith 



I large spine, 3 smaller spines and 2 long setae on outside, 4 small 

 spines on inside; posterior margin with 5 sets of setae; lateral setae 

 mostly singly inserted. Coxal plates of pereopods 2 and 3 about 30 

 percent longer than broad, with 6 or 7 marginal setae each. Coxal 

 plate of pereopod 4 subquadrate, extending distally less than 50 per- 

 cent of the length of segment 2, marginally with 5 setae. Pereopod 

 7 about 55 percent as long as body, about equal in length to pereopod 

 6 and 30 percent longer than pereopod 5. Bases of pereopods 5-7 

 not much broader proximally than distally; distoposterior lobes poorly 

 developed. Dactyls of pereopods 5-7 about 1/3 the length of cor- 

 responding propods. 



Abdominal side plates nearly identical to those of S. pecki but with 

 a little less production in plate 1 and a little more convexity in pos- 

 terior margin of plate 3. Pleopod 1, inner ramus 40 to 45 percent 

 longer than peduncle. Uropod 1 : outer ramus about 90 percent as 

 long as inner ramus, about 60 percent as long as peduncle, armed uith 



II spines; inner ramus with 12 spines; peduncle \\ith 11 spines. Uro- 

 pod 2 : outer ramus about 2/3 as long as inner ramus which is in turn 

 about equal in length to peduncle, armed with 5 spines; inner ramus 

 with 11 spines; peduncle with 5 spines. Uropod 3, ramus about 50 



