1951] 
Christiansen — Alaskan Collembola 
31 
antennae) — 1.26, cephalic diagonal — .26, thoracic segment 
2 — .17, seg. 3 — .15, abdominal seg. 1 — .12, seg. 2 — .12, 
abdmn. seg. 3 — .12, abdmn. seg. .4 — .17, abdmn. seg. 5 — 
10, abdmn. seg. 6 — .05, antennal segment 1 — .03, ant. seg. 2 
— .04, ant. seg. 3 — .04, ant. seg. 4 — .08, unguis 1 — .026, 
empodial appendage 1 — .012, unguis 3 — .031, emp. app. 
3 — .015, manubrium — .08, dens — .04, mucro — .026. 
Segmental ratios for size range 1.18 — 1.30 mm.: 
(standard, thoracic segment 2—10) 
cephalic thoracic 
diagonal segment 
2 3 
mean ratio 14.9 10 3.8 
average deviation .5 X .4 
abdominal segment 
1 2 3 4 5 
6.4 6.7 7.1 9.6 5.3 
.3 .3 .3 .4 .3 
(standard, antennal segment 4=10) 
antennal segment 
12 3 4 
mean ratio 3.5 5.7 5.5 10 
average deviation .2 .2 .2 X 
(standard, unguis 3=10) 
empodial 
unguis appendage 
13 13 
mean ratio 9.1 10 4.2 4.5 
average deviation .7 X .4 .3 
(standard, manubrium=10) 
manubrium dens mucro 
mean ratio 10 4.9 3.0 
average deviation X .3 .3 
6 
2.2 
.4 
Type locality: 68°, 20' N., 151°, 30' W., Anaktuvuk, Alas- 
ka, July 7, 1949. The holotype (mounted on a slide in 
Salmon’s mixture) and seven paratypes are being depos- 
ited in the United States National Museum, Washington, 
D.C. Five paratypes are being deposited in the Museum of 
Comparative Zoology, Cambridge, Mass. 
This species has also been taken by Dr. Marie Hammer 
from Mount Richardson, just west of the Mackenzie Delta 
in Arctic Canada. 
Bibliography 
(Axelson) Linnaniemi, W. M. “Apterygoten Fauna Finlands, Allgemeiner 
Teil,” Acta Soc. Sci. Fennicae, T. 34, 1907. 
Stach, J., “The Apterygoten Fauna of Poland in Relation to the World- 
Fauna of this Group of Insects”, Polish Academy of Sciences and 
Letters, Acta Monographica Musei Historiae Naturalis, 1947; Family 
Isotomidae. 
Willem, V., In “Resultats du Voyage du S.Y. Belgica”, 1902. 
