1951] 
Christiansen — Alaskan Collembola 
27 
Longer straight erect setae (two to three times as long as 
the normal setae) positioned as follows : second thoracic seg- 
ment with a pair, one near each anterior lateral corner of 
the imbricate area; third thoracic segment with a similar 
pair, more posterior in position ; abdominal segments 1 and 
2 with a median lateral pair of somewhat shorter setae ; ab- 
dominal segment 3 with a median transverse row of four 
setae, with the more lateral setae being longer; abdominal 
segment four with an anterior and a posterior row of four 
setae each, with the more lateral setae again being the 
longer, anterior row of long setae about one-third of the way 
back from anterior border of the segment and the second 
row of somewhat shorter setae just before the posterior 
border of the tergite; on the fifth segment a single median 
transverse row of setae; and sixth segment with four long 
setae and numerous short straight ones. Fifth abdominal 
segment dorsally with eight small spines on short papillae, 
arranged in two transverse rows of four each. 
A very small internal tooth is visible about midway up on 
the first pair of claws. No other teeth present. Empodial 
appendage stout, acuminate, with a broadly rounded inner 
lamella, and a well-developed apical filament. 
Manubrium with two ventral setae near the bases of the 
dentes and dorsally with twenty straight smooth setae ar- 
ranged in two irregular double rows, confluent basally, then 
running down the outer sides of the manubrium so as to 
leave a distal, central, triangular, naked area. Dens dorsally 
with a single low, broad hump and five setae, positioned as 
follows : one at base of the dens, three forming a centrally 
positioned triangle, and a fifth short curved setae ventraliy 
just before the mucro. Dens abruptly narrowed at the end 
and distinctly wider than the mucro. Mucro distinctly sep- 
arated from dens, tridentate, slightly curved and somewhat 
larger basally. Basal tooth distant from the apical and sub- 
apical teeth. Subapical tooth pointed upward and distinctly 
larger than the apical and basal teeth which are subequal. 
Apical tooth pointed forward and only slightly curved. 
Genital plate of male simple, not clearly demarcated, and 
