558 PROCEEDINGS OF THE NATIONAL MUSEUM vol. us 



3, that of legs 3-4 longer than exopod 3 (leg 3, from 1.02 to 1.10:1; 

 leg 4, from 1.08 to 1.17:1); inner apical seta reaching almost to end 

 of or a little beyond inner spine in leg 2, shorter than spine in legs 3-4. 

 (Measiu'ements of exopod segments in midline, exopod 1 measured 

 from exact base which is inserted deeply into basal segment 2; in 

 above ratios, exopod 3 expressed as 1). 



Leg 5 (figs. 2a, 6): Exopod segment 1, outer spines variable in 

 length, first usually longer than width of segment, second as long as 

 first spine or shorter; outer margin of segment constricted distad to 

 insertion of first spine; inner process slender throughout, du-ected 

 inwards, tip upcurved and finely serrate, about 4 X width of distal 

 part of segment (process measured from notch near base to its tip; 

 segment from notch of process to insertion of distal spine). Exopod 

 segment 2 slender, length less than twice width (about 1.7:1); 

 length of outer apical spine variable, ranging from about one-half to 

 a little more than that of segment (figs. 2a and 26 show extremes) ; 

 inner apical spine elongate, shorter than or subequal to total exopod 

 length and ranging from 5.6 to 7 X length of segment 2 and from 

 3.2 to 4.8 X that of outer spine; segment not produced to sharp point 

 between spines, with or without setule on inner margin. 



Copepodid stage V: Total length (1 specimen, Lake 4, July 28, 

 1960): 1.72 mm. (metasome, 1.025; urosome, 0.695). Cephalic pro- 

 tuberance present. Metasomal wings shorter than in adult but of 

 similar form. Proportional length of urosome segments similar to 

 adult, but caudal rami shorter, their length less than segments 2 + 



3 (0.8:1), width about 4 X length; genital segment without lateral 

 protrusions. Antennules a little shorter than metasome. Leg 5 

 (fig. 2b) : Inner process of exopod 1 a little longer than width of 

 segment. Length of specimens from Umiat less than that of Lake 4 

 specimen (1.32-1.43 mm.); length of theu' caudal rami subequal to 

 or only a little less than urosome segments 2 + 3. 



Description of male.— Total length: 1.56-1.65 mm. Greatest 

 width of metasome in segments 2-3; distal segments not so narrowed 

 as in female. Distal cephalic protuberance present. Urosome (fig. 

 3/) without ornamentation; segment 4 the shortest, segment 5 the 

 longest. Caudal rami: Length subequal to urosome segments 3 + 



4 + 5, about 7 X greatest width; with inner marginal and outer 

 distal hairs but no surface ornamentation; caudal setae similar to 

 those of female, lateral seta subequal to and others longer than rami. 



Antennules reaching a little beyond metasome. The left differmg 



Figure 2. — Eurylemora arctica, new species, female (appendages drawn to same scale): 

 a and c, leg 5, adult, showing variation in outer spines and detail of bases of exopod 3 

 spines; b, leg 5, copepodid stage V; d, leg 2; e, leg 1;/, leg 3, exopod 3; g, leg 4. 



