84 U.S. NATIONAL MUSEUM BULLETIN 2 59 



10 spines; peduncle with 5 spines. Uropod 3, ramus about 35 percent 

 as long as peduncle, armed with 2 apical spines. Telson elongate, a 

 little more than 50 percent longer than broad; apex sUghtly convex 

 and armed with 10 unequal spines, the longer outermost spine on 

 either side deflected laterally from the midhne and possessing 1 or 2 

 small, distal tines. 



Female. — Generally similar to male but differing in several 

 important details as follows: Antenna 1 approximately 65 percent 

 as long as body and up to 50 percent longer than antenna 2, primary 

 flagellum mth 26 segments, Gnathopod 1 : propod palmar margin 

 teeth smaller; posterior angle with 1 large spine and 4 smaller spines 

 on outside, 5 spines on inside; lateral setae greater in number, superior 

 lateral setae doubly inserted, inferior lateral setae singly inserted. 

 Gnathopod 2: propod palmar margin straight, armed with a double 

 row of 9 small spine teeth; posterior angle mth 1 large spine and 3 

 smaller spines on outside, 3 small spines on inside. Abdominal 

 side plates 2 and 3 with 3 or 4 ventral marginal spines each. Uropod 

 3, ramus armed Avith 1 distolateral spine and 3 unequal, apical spines. 

 Telson about 40 percent longer than broad, apex convex and armed 

 with 12 unequal spines. 



Type locality. — Springs on Rich Mt., Rich Mt. Station, Polk Co., 

 Ark. The type locality is approximately situated in the geographic 

 center of the Ouachita Mountains where the surrounding geological 

 horizon appears to be Mississippian sedimentary rocks of largely 

 sandstone and shale facies. 



Distribution and ecology. — This species is known only from 

 its type locality and ^drtually nothing is known about its distri- 

 bution and ecology. 



Remarks. — Although Hubricht and Mackin (1940) referred to the 

 Rich Mountain collection as a "distinctive lot," they failed to recog- 

 nize this material as a separate species. There appears to be no 

 good reason, however, why this material should not be considered 

 specifically distinct. 



Stygonectes elatus, new species 



Figure 20 



Synpleonia dantoni Greaser. — Hubricht, 1943, p. 711 (in part). 



Material examined 



ARKANSAS. — Logan Co.: seep, 0.2 mUe E of The Lodge, Magazine Mt., female 

 holotype, male allotype, 2 female paratypes, L. Hubricht, May 4, 1940 (USNM) 



Diagnosis. — Distinguished from S'. montanus, which it closely 

 resembles in several important aspects, by having several slender 

 ventral spines on peduncular segment 4 of antenna 2, straight propod 



