1951] 
Christiansen — Alaskan Collembola 
131 
Pseudanurophorus arctica, n. sp. 
(PL 10, figs. 12-14; PL 11, figs. 1, 3-5) 
Holotype. Body stout, cylindrical, rounded posteriorly, 
head about as wide as body. Without eyes or pigment. 
Clothing of scattered short, straight to weakly curved 
setae with a few longer straight setae, especially on the 
posterior regions of the body. Common setae of the head 
are from nine to twelve micra in length and more or less 
curved. There is also a single row of fifteen micra long 
setae along the posterior margin of the head. 
First thoracic segment is naked dorsally and has a 
single pair of setae at each leg base, with the superior 
seta of each pair longer than the inferior. On each leg 
base of the second and third pair there is a set of four 
long setae. The remainder of the thorax and the abdomen 
is clothed mostly with short, curved to straight setae, 
one-half to three-fourths as long as long setae, with the 
smaller sizes being much more numerous. Besides these 
there are a few long setae, arranged as follows : second and 
third thoracic segment with a single seta at each lateral 
edge of the setaceous area; first and second abdominal 
segments each with a single medio-lateral pair of setae, 
with those on the second segment being slightly longer; 
third and fourth abdominal segments with four setae each, 
situated in lateral pairs, the anterior of each pair being 
slightly longer; fifth abdominal segment with a posterior 
row of four setae which are longer than any anterior body 
setae, and a single anterio-lateral shorter seta on either 
side; sixth abdominal segment with eight long setae. 
Integument finely and uniformly granulate. Unsetaceous 
intersegmental membranes large between all segments 
except the fifth and sixth. 
Fourth antennal segment fusiform, third somewhat 
spheroidal in appearance, and the second and first seg- 
ments sub-cylindrical in shape. Fourth antennal segment 
with numerous obtusely pointed “olfactory” hairs, slightly 
thicker than, and subequal in length to, the normal clothing 
setae. Sense organ of third antennal segment consists of 
two blunt rods situated in shallow integumentary folds, 
the inner being somewhat above the outer. 
