New Alaskan Records of Eurytemora (Crustacea, Copepoda) 
I 
Mildred Stratton Wilson^ 
The copepod genus Eurytemora is known 
from all the coastal areas of North America, 
though the records are not extensive. The 
species occur in salt, brackish, and fresh water. 
As the genus is widely spread throughout the 
northern regions of the world, it is to be 
expected that the coastal areas of Alaska 
would have an abundance of all the habitat 
forms. Unfortunately, in the Alaskan collec- 
tions made during the Canadian Arctic Ex- 
peditions no mature specimens were found 
(Marsh, 1920: 4j). The present report is there- 
fore of interest in recording two species from 
western Alaska. These include a fresh-water 
form new to science and an Asiatic brackish- 
water species not before known in North 
America. 
I am indebted for these collections to Dr. 
Clifford O. Berg of the Arctic Health Re' 
search Center and to Mr. Frank P. Pauls of 
the Alaska Department of Health. Specimens 
of each species have been deposited in the 
United States National Museum. 
Eurytemora yukonensis n. sp. 
Figs. 1-5 
SPECIMENS EXAMINED. Four lots, fresh wa- 
ter, lower Yukon River area, western Alaska. 
C. O. Berg, collector. 
Type lot: 25 9 (many ovigerous); 13 cf ; 
many copepodids. Wilson Creek, about a mile 
southeast of Fortuna Fedge (formerly and 
popularly known as Marshall), July 27, 1951. 
1 Arctic Health Research Center, United States Pub- 
lic Health Service, Federal Security Agency, Anchorage, 
Alaska. Manuscript received October 10, 1952. 
Holotype 9, U.S.N.M. 93268; allotype ci^, 
U.S.N.M. 93269. 
Lot 2: A 9,5 cf, many copepodids. Near 
outlet of stream into Yukon River, about 14 
mile north of Fortuna Fedge, July 28, 1951. 
Lot 3: A 9 , copepodid stage V. Small lake 
southwest of Holy Cross, June 15, 1951. 
Lot 4: 1 9 , 8 d^, 4 copepodids. Widened 
portion of stream emptying into Andreafsky 
River, about 1 mile east of Andreafsky, Au- 
gust 16, 1951. 
Female: Total length, dorsal mid-line, 
1.645 mm. (metasome 1.01 mm., urosome 
0.635 mm.). Head rounded, body tapering, 
the greatest width in segment 2 (0.415 mm.); 
width of segment 5, 0.34 mm. First segment 
showing in lateral view (Fig. 1) a pronounced 
cephalic depression and a prominent medial 
distal protuberance. "'Wings” of last segment 
very wide, slanting outward, without pro- 
nounced inner lobes, entire expanse greater 
than width of second segment (0.48 mm.), 
Urosome equaling 38 per cent of total 
length. Relative lengths of segments and 
caudal rami, exclusive of caudal setae: 
1 2 3 CR 
50 33 45 61 
Genital segment constricted in middle, a 
little asymmetrical, both proximal and distal 
lobes prominent, proximal wider than distal, 
both armed with a few lateral sensory hairs. 
Genital operculum small, nearly hemispheri- 
cal, distal edge quite rounded. Segments 2 
and 3 without ornamentation. 
Caudal rami shorter than segments 2 and 
3 combined, their length about 5.5 X their 
width; unarmed except for inner marginal 
504 
