114 U.S. NATIONAL MUSEUM BULLETIN 259 



lobes medium size to small. Propod of gnathopod 1 about equal in 

 size to that of gnathopod 2 but a little broader. Palmar margins of 

 gnathopodal propods straight to convex. Bases of pereopods 5-7 

 relatively narrow, not broadly expanded; distoposterior lobes poorly 

 developed. Pereopod 7 about equal to pereopod 6 in length, 25 to 

 35 percent longer than pereopod 5. Median sternal and pleonite 

 sternal gills absent; lateral sternal gills simple; all other gills present. 

 Abdominal side plates: posterior margins not broadly convex, those 

 of plates 1 and 2 relatively straight; posterior corners distinct except 

 in plate 3 of S. jiagcllatus. Uropod 2 proportionately rather long. 

 Telson elongate, gently narrowing distally. 



Relationship. — The flagellatus group bears resemblance to the 

 emarginatus group as indicated by the near equality in size of the 

 gnathopodal propods, nearly equal length of pereopods 6 and 7, shape 

 of pereopod bases, rather long uropod 2, and the fact that mature 

 females are typically larger than mature males. 



On the basis of morphology, the flagellatus group has been divided 

 into two rather divergent subgroups, one of which is known only from 

 females and which must await the discovery of males before its exact 

 taxonomic affinities are clear. 



Distribution and ecology. — This group is composed of four rare 

 species, and to date only one of these species has been found outside 

 of its type locality. The flagellatus group is largely of cavernicolous 

 affinity and occupies a relatively small geographic area in central 

 Texas as follows: two species are known from one cave each in south- 

 eastern Kendall County, a third species has been taken from a spring 

 outlet 35 miles further east in Comal County, and a fourth species is 

 known from a cave and a nearby, related artesian well in southeastern 

 Hays County. 



Key to Species in the flagellatus Group 



1. Antennae and pereopods elongate; 1st antenna 75 to 100 percent as long as 



body; pereopods 6 and 7 between 60 and 70 percent as long as body; telson 



with lateral spines {flagellatus subgroup) 2 



Antennae and pereopods not especially elongate; telson without lateral 

 spines (pecki subgroup) 3 



2. Antenna 1 usually about twice as long as antenna 2; basis of pereopod 5 



expanded proximally; subterranean Purgatory Creek System in Hays Co., 



Tex S. flagellatus (Benedict) 



Antenna 1 about 3 times as long as antenna 2 ; basis of pereopod 5 not expanded 

 proximally; single cave in Kendall Co., Tex. . . . S. longipes Holsinger 



3. Palmar margins of gnathopodal propods with rather small spine teeth; 



dactyls of pereopods 5-7 about 1/3 as long as corresponding propods; 3rd 

 uropod with 3 or 4 apical spines; Cascade Cave, Kendall Co., Tex. 



S. dejectus, new species 



