SUBTERRANEAN AMPHIPOD STYGONECTES 77 



Apr. 8, 1939; small seep in Boston Mts., 9.6 miles S of Boxley, Apr. 8, 1939; 

 Searcy Co.: small seep, 4.1 miles W of Marshall, Apr. 9, 1936; small seeps, 3.0 

 miles E of Harriet, Apr. 9, 1939; Stone Co.: seep near Blanchard Falls, J. R. 

 Holsinger and S. Peck, June 27, 1964 (JRH); Van Buren Co.: seep, 5.5 miles 

 N of Winslow, May 7, 1940. Tennessee. — Tipton Co.: seep, 4.4 miles SW 

 of Crosstown, Feb. 26, 1961. Mississippi. — Lauderdale Co.: seep in ravine, 

 4 miles SE of JNIeehan, Mar. 29, 1964; seep at 3708 Royal Rd., Meridian, Mar. 

 31, 1963; seep, 2.7 miles S of Meridian, Apr. 22, 1962; seep in ravine, 1 mile S 

 of Meridian, Oct. 8, 1961; seep, 3 miles SE of Whynot, Mar. 29, 1964; seep, 2 

 miles SE of Whynot, Feb. 3, 1963. Missouri. — Barry Co.; Crystal Cavern, 

 May 8, 1940; Laclede Co.: seep near Bennett Spring, May 16, 1942; Coffin 

 Cave, O. Hawksley, Feb. 6, 1960; Newton Co.: Big Spring, Neosho, May 9, 

 1940; Pulaski Co.: temporary spring, 0.5 mile W of Hooker, May 10, 1942; 

 Bat Cave, 5 miles S of Crocker, Aug. 17, 1940; Riden Cave, 2 miles W of Duke, 

 June 7, 1942; Stone Co.: Marvel Cave, C. Mohr, Dec. 26, 1935; Wright Co.: 

 Smittle Cave, 5 miles N of Grove Spring, June 4, 1940. Oklahoma. — Mayes 

 Co.: seeps, 4.6 miles W of Locust Grove, May 22, 1940; Latimer Co.: seeps, 

 in San Bois Mts., near Wilburton, J. G. Mackin, Apr. 28, 1931 (paratypes of 

 Bourta americana, USNM Ace. No. 137144). 



Diagnosis. — -Medium-sized interstitial and cavernicolous species 

 distinguished from other species in the tenuis group, except S. barri, 

 S. balconis, and »§. tenuis, by the deeply concave palmar margins of the 

 gnathopods (especially in males). Further distinguished from S. 

 barri by lack of lateral spines on telson, from S. balconis by generally 

 smaller size at maturity and fewer spine teeth on gnathopodal propods, 

 and from S. tenuis by the smaller 2nd antenna of larger males. Dif- 

 ferentiated from S. a. occidentalis , new subspecies, by the diagnosis 

 given for that subspecies. Largest males, 13.50 mm; largest females, 

 9.75 mm. 



Male. — Antenna 1 generally between 60 and 75 percent as long as 

 body (but varying between the extremes of 53 and 100 percent), up 

 to 65 percent longer than antenna 2; primary flagellum with up to 38 

 segments (28 to 38) ; accessory flagellum relatively long, extending as 

 far distad as the first 2 primary flagellar segments. Antenna 2, 

 flagellum with up to 10 or 1 1 segments. Palpal segment 3 of mandible 

 with 6 to 10 long setae, segment 2 with 6 to 9 setae. Maxilla 1, 

 inner plate with 4 to 7 apical, plumose setae. Maxilla 2, inner plate 

 with 4 to 6 long, obliquely placed, plumose setae. Maxilliped: inner 

 plate with 3 or 4 (usually 4) thick spines apically; outer plate extend- 

 ing nearly to apex of 1st palpal segment. Lower hp, inner lobes 

 rather broad. 



Gnathopod 1: propod palmar margin deeply concave, armed with 

 a double row of 6 or 7 spine teeth; posterior angle with 1 large spine, 

 3 or 4 smaller spines and 1 set of setae on outside, 4 small spines on 

 inside; posterior margin with 3 sets of setae; lateral setae few in num- 

 ber, mostly singly inserted; dactyl claw rather long. Gnathopod 2: 

 propod palmar margin a Uttle less deeply concave but armed similarly 



