560 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iia 



from female in more distinct separation of segments 8-9 and in having 

 only 1 seta on segment 11 and sometimes 2 setae on segment 4 (this 

 latter possibly an anomaly) ; aesthetes on all of segments 1-19 except 

 on 4; setae not as long as those of female; many of the aesthetes 

 more developed than in female (fig. 36), those of segments 13, 15, 

 and 17 unusually stout and elongate, each reaching almost to end of the 

 succeeding 3 segments. Right antennule: Spines of segments 8-12 all 

 very short (fig. 3c), not more developed than reduced spines of seg- 

 ments 8, 10, and 12 of left antennule; aesthetes of segments 13 and 15 

 stout and elongate (fig. 3a), reaching beyond succeeding 2 segments; 

 apical portion beyond geniculation 2-segmented, subequal in length 

 to combined segments 15-18; approximate ratio of lengths of last 

 4 segments (segment 17 expressed as 1): 1:1.4:2:2.6. 



Mandible blade and legs 1-4 similar to female. 



Leg 5 (figs. Sd, e; drawn from legs mounted in shallow depression, 

 slides so that structural features not distorted by cover glass pressure) : 

 First basal segments fused, remnant of connecting plate present; 

 left longer than right; right mth inner marginal lobes. Right leg: 

 Basal segment 2 \^dth small inner proximal lobe, distal part of segmenti 

 broadened inwardly; exopod 1 with prominent inner distal swelling; 

 exopod 2 only a little longer than exopod 1, constricted near middle 

 but without segmental separation in any observed specimens, basal 

 part broader than distal and with marginal sclerotization and short! 

 inner and outer spines, narrowed distal part a little longer than basal. 

 Left leg: Inner proximal portion of anterior face of basal segment 2 

 sclerotized (or cuticle thickened), forming narrow plate produced 

 into spinous point; outer spine of exopod 1 longer than width of seg- 

 ment; exopod segment 2 a little longer than right exopod 2, distal por-' 

 tion broadened beyond middle, apex irregular in shape but without i 

 prominent protrusion and armed with very short spinules. 



Copepodid stage V: Total length range: 1.275-1.56 mm. (Lake 4, 

 1.38-1.46 mm.; Lake 3, 1.56 mm.; Umiat, 1.275-1.40 mm.). Form! 

 of metasome similar to adult; cephalic protuberance not prominent. 

 Urosome 4-segmented, last segment (= segments 4 + 5 of adult) 

 subequal in length to segments 2 + 3; caudal rami subequal to seg- 

 ments 3-5, as in adult. Antennules reaching to end of metasome or a 

 little beyond. Leg 5 (fig. 3^) : Spines of exopod segments stout; inner 

 apical spine longer than outer, that of left side longer, usually more 

 than one-half length of segment (a single specimen collected from 



Figure 3. — Eurytemora arctica, new species, male (appendages drawn to same scale): 

 a, right antennule, from segment 7 to apex; h, left antennule, segments 11-20; c, right 

 antennule, spines of segments 8-12; d and e, leg S, adult, anterior view (from 2 specimens 

 in slightly different positions and undistorted by cover glass pressure); f, urosome, dorsal; 

 g, leg 5, copepodid stage V, posterior view. 



