98 FOLSOM [ IO ] 



are only two 5n typical niger', as I have implied, however, arcticus is 

 connected with niger through americanus ; in fact, the variety of 

 arcticus with two basal spines might be called americanus, were its 

 true relations with arcticus not known. 



The dental scales also, occurring in no other described species ex- 

 cept T. plumbeus, are of significant value. 



To summarize : arcticus varies into americanus which, in turn, 

 connects insensibly with niger. The first two, then, are properly to 

 be called varieties of niger {flavescens) the first described of the 

 three. The question whether niger is actually nearest the stem form 

 a debatable subject, which I have but partially settled fortunately 

 does not affect the terminology to be adopted. 



Although niger has long been known to occur throughout Europe 

 under the name of flavescens, it has not been hitherto recorded from 

 the Arctic regions. 



TOMOCERUS NIGER Bourl., var. ARCTICUS Schott. 



(PI. vra, figs. 48-52.) 



Tomocerus arcticus ScnSTT, K. sven. vet. akad. hand., xxv, No. n, p. 43, taf. 

 3, figs. 8, 9, 1894. DALLA TORRE, Die Gattungen und Arten der Ap- 

 terygogenea (Brauer), p. u, 1895. ^CHAFFER, Fauna Arctica, I, lief. 2, 

 p. 251, 1900. 



Typical arcticus is citron yellow, when denuded of scales. Eyes 

 six on either side (fig. 48), as usual. Antennas over three times as 

 long as the head, or two-thirds the length of the body ; segments re- 

 lated as 2:3 : 1 3 : 3 ; basal ring purple ; first two segments yellow, 

 second often purplish distally ; last two pale purple. Prothorax con- 

 cealed ; remaining segments related in length as 8:6:5:6:9 .-6:3:2. 

 Legs yellow throughout, or else coxa? and tibia? purplish ; superior 

 claws (fig. 49) rather stout, slightly curved, pseudonychiate ; inner 

 margin distinctly quadridentate, as a rule ; superior claws of hind feet 

 one-third longer than those of the other feet ; inferior claws two-thirds 

 as long as the large claws, lanceolate, acute, inner margin unidentate 

 two-fifths from the apex ; tenent hair knobbed. Furcula attaining the 

 ventral tube ; segments as 5:7 : i , in relative lengths ; manubrium 

 yellow, remainder white. Dental spines (fig. 50) normally six or 

 seven on either side, becoming successively smaller proximally ; distal 

 spine more lateral than the rest ; two large ovate-lanceolate acuminate 

 transparent scales occur near the manubrium. Clothing as in T. 

 niger, type. Length, 3.5 mm. 



One specimen, Popof Id., 1899 (No. 96); four, Cook Inlet, 1899 



