490 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 50. 



Unguis (fig, 91) unidentate near the middle of the inner margin. 

 Unguiculus about haK as long as unguis, with rounded or suboblong 

 basal lamella and with apical two-thirds tapering to a point. Tenent 

 hair single, unknobbed. Mucrones two-fifths as long as dentes, 

 almost as long as hind ungues, somewhat slipper-shaped, the outer 

 lamella having a prominent obtuse angle, as in figure 92, Anal 

 spines (fig. 93) long, exceeding the hind ungues in length, slender, 

 curving, separated basally. Clothing (fig. 94) of short curving setae 

 and short stiff hairs. Length, 1 mm. 



This species referred to A. longisjnnus Tullberg by Guthrie, is 

 distinct from that species, as I have found by comparing 20 of 

 Guthrie's specimens with 6 Spitzbergen examples of longisjnnus 

 given to me by Doctor Schaffer. In longispinus the mucrones are 

 spoon-shaped and tuberculate, and the body setae differ from those 

 of this species in form, number, and arrangement. 



A. guthriei is allied to A. hengtssoni Agren ('04, p. 2j in the form of 

 the mucrones; but the latter species is olive brown, with short anal 

 spines, apically swollen dentes, eversible sac between the third and 

 fourth antennal segments, and other characters different from those 

 of this species. 



A. guthriei is also related to but evidently distinct from A. 

 sigillatus Uzel ('90, p. 70). 



Tlie preceding description is based on 20 of Guthrie's specimens 

 (slide No. lS5d, Univ. of Minn.), collected by him August 23, 1899, 

 at Lake Pepin, Minn., where they occurred by hundreds on the sur- 

 face of a pool of water. 



The cotypes of A. guthriei are in the collection of the University of 

 Minnesota. 



ACHORUTES PSEUDARMATUS, new species, 



Plate 14, figs. 95-100; plate 15, figs. 101-103. 



Black or mottled dark blue. Eyes, eight on each side (fig, 95). 

 Postantennal organs (fig, 95) with four peripheral tubercles and a 

 conspicuous round "Nebenhocker"; the two anterior peripheral 

 tubercles are twice as long as the posterior ones. Antennae subequal 

 to head in length. Olfactory hairs of fourth antennal segment 

 (fig. 96) seven in number — two outer, two inner, and three dorsal. 

 Sense organ of third antennal segment as in figure 97, There is no 

 eversible sac between the third and fourth antennal segments. 

 Unguis (fig. 98) long, slender, slightly curving, unidentate near the 

 middle of the inner margin; lateral margins each unidentate one- 

 third from the base, Unguiculus extending half as far as the unguis, 

 with rounded basal lamella and acuminate apical half. One long 

 tenent hair, feebly clavate. Dentes stout, apically rounded. 

 Mucrones (figs. 99, 100) three-fifths as long as dentes, in form much 

 like those of armatus, but with the outer lamella terminating distally 



