18 h Canadian Arctic Expedition, 1913-18 



whereas in Cryophilus it opens freely through the mesal margin of the sclerite, 

 the cauclomesal lobe not extending forward to its level. 



Cryophilus alaskanus, n. sp. 



Colour fulvous throughout, the head of dilute ferruginous cast. 



Body strongly narrowed caudad over posterior third, scarcely at all nar- 

 rowed cephalad. 



Cephalic plate widest in front of middle, sides evenly convex; anterior 

 margin wide, arcuate, being concave on each side and protruding slightly 

 between the antennae; caudal margin truncate or very weakly convex. Longer 

 than wide in ratio 22 : 17. Hairs very few and widely scattered, short. 



Antennae short, attenuated distad, 2-25 times longer than the cephalic 

 plate. Last article of same length as the two preceding ones taken together. 



Basal plate overlapped in front by the cephalic, its exposed area being 

 4 or 4 • 25 times wider than long. 



Claws of prehensors when closed attaining or a little exceeding the distal 

 end of the first antennal article. Claw armed at base with an acute, conical, 

 only slightly darkened tooth. Femuroid armed at distal end with a smaller 

 distally rounded tooth. The intermediate joints with smaller nodules. 



Anterior margin of prosternum unarmed mesally slightly concave. Sides 

 in front of rounded caudal cornes straight, slightly diverging cephalad. A 

 little wider than long, the ratio being 9 : 8. Nearly 1 • 7 times longer than the 

 height of femuroid on its ectal side. 



Paired sulci of tergites deep. On some plates a pair of weaker intermediate 

 sulci may be present but on most such are absent. 



Presenta in anterior region short. Increasing in length to posterior end 

 of middle region where they are moderately long, always less than half as long- 

 as the principal plate, the ratio not exceeding 1 :2-5. Again decreasing in 

 caudal region. 



Spiracles all circular, moderate or small, decreasing gradually caudad. 



Anterior ventral plates with a median longitudinal sulcus, the others 

 without sulci. First seven plates with caudad margin angularly produced at 

 middle, the process fitting into an excavation in the succeeding plate. 



No ventral pores detected. 



Legs of first pair very little smaller than the second ones. 



Last ventral plate trapeziform. Caudal and lateral margins straight. 

 Plate with width across anterior end equal to the length. 



Pores of caxopleurae small, about fourteen in number on each side; mostly 

 near edge of ventral plate, a few isolated on side. 



Anal legs, exclusive of caxopleurse, not or scarcely longer than the penult, 

 moderately crassate in the male; clothed with few long hairs and on ventral 

 surface in the male with more numerous, fine short ones; clawless. 



Pairs of legs, thirty-nine. 



Length, 18-20 mm. 



Locality : Nome, Alaska. Two specimens taken August, 1916. The 

 field label states that the specimens were secured " under logs on tundra," and 

 Mr. Johansen, the collector, notes in his journal that the species occurred " under 

 loose stones, boards, etc., on tundra near town." 



Aside from the differences indicated under the account of the genus, this 

 species differs from A. glacialis, as described and figured in the original account, 

 in various characters. Thus, the figure and text show the lappets of the first 

 maxillae of A. glacialis to be short, thick, and equal; in the present species they 

 are much longer and proportionately more slender, that of the coxa being at 

 the same time shorter and more slender than that of the succeeding joint, and 

 the second lappet extending beyond the tip of the second joint of the branch, 

 though falling much short of it in glacialis. The median region of the united 



