SUBTERRANEAN AMPHTPOD STYGONECTES 17 



section is cuiTently held in abeyance pending a planned generic 

 revision. 



Genus Stygonectes Hay 



Figure 1 



Stygonectes Hay, 1903, p. 430. [Type species, by original designation, Crangonyx 



flagellalus Benedict, 1896.] 

 Synplconia Creaser, 1934, p. 1. [Type species, by monotypy, Synpleonia clantoni 



Greaser, 1934.] 



Diagnosis. — Without eyes or pigment; known only from sub- 

 terranean and interstitial habitats. Size of sexually mature adults 

 ranging from about 4.50 mm to 19.50 mm. Antenna 1: longer than 

 antenna 2, with exception of S. tenuis (Smith) in which antenna 



2 exceeds length of antenna 1 in larger males; ranging in length from 

 less than one-half to sometimes (but rarely) as long as body; segment 

 1 of peduncle with several small spines on ventral margin; small 

 calceoli usually present on most primary flagellar segments; accessory 

 flagellum short, 2-segmented. Antenna 2: peduncular segments 

 4 and 5 about equal in length, segment 4 and sometimes 5 with several 

 pairs of small spines on inner face; small calceoU usually present on 

 most flagellar segments. Interantennal lobe distinct, rounded 

 anteriorly. Mandible: molar typicaUy well developed; 1st segment 

 of palp short, 2nd and 3rd palpal segments subequal in length, segment 



3 with a number of long apical setae. Maxilla 1: inner plate with 

 a number of long, apical plumose setae; outer plate with tj^iicaUy 

 7 serrate spines apically; palp 2-segmented and bearing apical setae. 

 MaxiUa 2: inner plate broader than outer plate, bearing a row of long, 

 obliquely placed, plumose setae. Maxilhped: inner plate sub- 

 rectangular, armed apicaUy with several thick spines and 1 to several 

 setae; outer plate reaching nearly to or just beyond apex of 1st palpal 

 segment, bearing coarse setae on apex and inner margin and often 1 or 

 rarely 2 apical spines; palp well developed, segment 2 the longest. 

 Outer lobes of lower Up broadest proximally, narrowing distally; 

 inner lobes varying from small to moderately broad, but vestigial 

 or absent in one species. 



Gnathopod 1: propod stouter and as large as and often larger 

 than propod of gnathopod 2, palmar margin armed with a double 

 row of notched spine teeth; coxal plate rather narrowly rounded 

 ventroanteriorly, margin with several setae. Gnathopod 2: propod 

 palmar margin with a double row of notched spine teeth; segment 5 

 about equal in length to combined lengths of segments 3 and 4. 

 Posterior margins of segment 5 of gnathopods commonly with 1 or 

 several rastellate setae (excepting the spinatus group and 6 of the 

 7 species of the emarginatus group). Pereopods 3 and 4 subequal 



