SUBTERRANEAN AMPHIPOD STYGONECTES 57 



Propod palmar margin of gnathopod 1 slightly concave in both sexes; 

 posterior margins of bases of pereopods 5-7 more convex; telson of male 

 with up to 20 untined, apical spines; known only from a single spring in 

 Washington, D.C S. hayi (Hubricht and Mackin) 



4. Telson with lateral spines 5 



Telson without lateral spines 6 



5. Propod palmar margins of gnathopods rather deeply and evenly concave; 



telson with up to 10 apical spines; seeps in Wayne and Madison Counties, 



Mo S. barri, new species 



Propod palmar margins of gnathopods not deeply or evenly concave; telson 

 with up to 20 apical spines; subterranean waters in southwestern Ozark 

 Plateau region S. ozarkensis, new species 



6. Telson armed apically with about 25 rather short spines; large species with 



adults up to 18.00 or 19.00 mm; east-central Kansas and west-central 



Missouri S. clantoni (Creaser) 



Telson with up to 20 but usually fewer apical spines; small to moderately 

 large species 7 



7. Pereopod 7 not as long as pereopod 6; telson with up to 20 apical spines; 



known only from females from a single seep in Mayes Co., Okla. 



S. bowmani, new species 



Pereopod 7 a little longer than pereopod 6; telson with fewer than 20 apical 



spines 8 



8. Palmar margins of gnathopodal propods rather deeply concave; lateral 



sternal gills bifurcate or not 9 



Palmar margins of gnathopodal propods slightly concave to straight, never 

 deeply concave; lateral sternal gills bifurcate or not 10 



9. Lateral sternal gills simple, not bifurcate; telson of male with up to 10 apical 



spines; mature males up to 16.00 mm; single caves in Hays and Travis 



Counties, Tex S. balconis Hubricht 



Lateral sternal gills bifurcate; telson of male with up to 8 apical spines; 

 largest males up to about 13.50 mm; widely distributed from east-central 

 Alabama west to Dallas Co., Tex., and north to central Missouri. 



S. alabamensis (Stout) 



10. Propod palmar margins of gnathopods straight; lateral sternal gills not 



bifurcate 11 



Propod palmar margins of gnathopods slightly concave, straight, or sometimes 

 slightly convex; lateral sternal gills bifurcate 12 



11. Pereopods 5-7 relatively slender; pereopod 7 only 25 percent longer than 



pereopod 5; telson with up to 14 apical spines; known only from a single 



cave in San Saba Co., Tex S. reddelli Holsinger 



Pereopods 5-7 not as slender; pereopod 7 at least 30 percent (or more) 

 longer than pereopod 5; telson with up to 11 apical spines; caves of central 

 Texas S, russelli, new species 



12. Antenna 1 up to 50 percent as long as body; median sternal and pleonite 



sternal gills absent; adults rather large, up to 14.25 mm; caves of central 



Texas S. bifurcatus, new species 



Antenna 1 up to 65 or 75 percent as long as body; median sternal and usually 

 pleonite sternal gills present; adults smaller 13 



13. Peduncular segment 4 of 2nd antenna with a few slender spines on ventral 



margin ; propod palmar margin of gnathopod 1 straight, that of gnathopod 

 2 slightly convex; telson of female with up to 18 apical spines; known only 

 from a single seep in Logan Co., Ark S. elatus, new species 



