SUBTERRANEAN AMPHIPOD STYGONECTES 73 



Generally corresponding to the description by Hubricht and Mackin 

 (1940) with the following additions and modifications: 



Male.— Antenna 1 about 50 percent longer than body, not more 

 than 25 percent longer than antenna 2; primary flagellum with up 

 to 25 segments. Antenna 2 relatively long; flagellum with up to 13 

 segments, penultimate segment not enlarged or arcuate. Mandibular 

 palpal segment 3 with 7 or 8 long setae, segment 2 with 8 or 9 setae. 

 Maxilla 1, inner plate with 4 apical, plumose setae. Maxilla 2, inner 

 plate with 4 long, obliquely placed, plumose setae, Maxilliped, 

 inner plate with 3 or 4 thick apical spines. Inner lobes of lower 

 lip rather broad. 



Gnathopod 1 : propod palmar margin slightly concave, armed with 

 a double row of 8 or 9 spine teeth; posterior angle with 1 large spine 

 and 3 smaller spines on outside, 4 small spines on inside; posterior 

 margin short, with 4 sets of setae. Gnathopod 2: propod palmar 

 margin slightly concave or nearly straight, armed with a double row 

 of 7 or 8 spine teeth; posterior angle with 1 large spine and 3 small 

 spines on outside, 4 small spines on inside; posterior margin with 

 7 or 8 sets of setae ; coxal plate a little broader than long, with about 5 

 setae marginally. Coxal plate of pereopod 3 a little broader than 

 long, with 7 or 8 marginal setae; coxal plate of pereopod 4 about as 

 broad as long, with 7 or 8 marginal setae. Pereopods 5-7, bases 

 with moderately convex posterior margins. Dactyls of pereopods 

 about equal in length to those described for S. allegheniensis, a little 

 shorter proportionately than those of S. tenuis. Sternal gills absent 

 on 1st pleonite; all other gill structures present. 



Abdominal side plates: posterior margins convex, with 2 to 4 setae 

 each ; posterior corners rounded, indistinct ; ventral margins with 1 to 3 

 spines each. Pleopod 1, inner ramus nearly twice as long as peduncle. 

 Uropod 1 with about 40 spines. Uropod 2 with about 25 spines. 

 Telson about twice as long as broad, armed apically with 18 to 20 un- 

 equal spmes, the outermost being untined and undeflected laterally. 



Female. — Differing from the male as follows: Antenna 1 with 22 to 

 25 primary flagellar segments. Antenna 2 only about 2/3 as long as 

 antenna 1, with 10 or 11 flagellar segments. Gnathopod 1: propod 

 palmar margin slightly concave, armed with a double row of 8 or 9 

 spine teeth; posterior angle with 1 large spine and 5 smaller spines on 

 outside, 5 small spines on inside; posterior margin with 3 or 4 sets of 

 setae. Gnathopod 2: propod palmar margin nearly straight, armed 

 with a double row of about 7 small spine teeth; posterior angle with 

 1 large spine and 4 smaller spines on outside, 5 small spines on inside; 

 posterior margin with 7 or 8 sets of setae. All gill structures present. 

 Uropod 1 with about 8 more spines. Uropod 2 with 7 or 8 more spines. 

 Telson with about 18 unequal, apical spines. 



