190 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 112 



Description op the female: Body 2.65 mm. in length (mean of 

 6 specimens, range 2.54-3.0 mm.). Prosome narrower (0.89 mm., 

 0.84-0.94 mm.) in proportion to its length than in any of the other 

 species; terga separated, their corners rounded. Urosome more than 

 twice length of prosome. Ovisacs long and narrow. First 3 ab- 

 dominal segments with narrow ventral membrane posteriorly; anal 

 segment with row of small spinules along posterior border. 



Length of caudal rami about 3 times width; hairlike element on 

 outer side near base less well-developed than in H. adhaerens or 

 subadhaerens. 



Antennule as in figure 9b. Curved seta on outer side of slightly 

 protruding distal corner on third segment of antenna rather stouter 

 than in the other species; spines on tip of projection like those of 

 thysanotus. Inner faces of second and third segments swollen; with 

 large patches of regularly arranged spinules; rows of larger spinules 

 (which have a peculiar flattened and frayed appearance) on outer 

 sides third and terminal segments. 



Spinules on labrum confined to a row along each edge. Paragnath 

 with cutting edge notched; row of long cilia on posterior surface not 

 as well developed as in adhaerens. Labium with very fine spinules 

 confined to raised median portion which abuts on roof of mouth 

 cavity; occasionally a row of small denticles on each side behind these. 



Mandible may have no trace of a second seta in addition to curved 

 element and blade. Latter somewhat curved, unlike condition in the 

 other species. 



Maxillule much like that of adhaerens but with well-developed 

 anterodorsal prominence. 



Terminal armature of maxilla similar to condition in adhaerens; 

 setule-bearing seta on first segment even more enlarged. On one 

 maxilla of holotype, armature on this segment is that shown on inset 

 to figure 9h. 



Figure 9. — Hemicyclops arenicolae, new species, female: a, Habitus, dorsal aspect, b, Left 

 antennule, ventral (posterior) view, c, Left antenna, dorsal (posterior) view, d, Second 

 and third antennal segments, lateral (outer) view, e, Mouth area (without appendages), 

 ventral view. /, Right mandible, ventral (posterior) view, g, Left maxillule, dorsomedial 

 (posteromedial) view, h, Left maxilla, ventral (posterior) view, with detail of unusual ele- 

 ment on basal segment of right maxilla, i, Left maxilliped, dorsal (anterior) view. /, Left 

 first swimming leg with coxal plate, ventral (anterior) view, k, Left second swimming 

 leg with coxal plate, ventral (anterior) view. /, Left third swimming leg with coxal plate, 

 ventral (anterior) view, m, Right fourth swimming leg with coxal plate, ventral (ante- 

 rior) view, n, Left fifth leg, ventral view. 0, Left sixth leg, dorsal view, p, Right 

 caudal ramus, dorsal view. Scale A (fig. 2) applies to a; C to b and j—n\ E to c—i and p; 

 and G to 0. 



