4 A Canadian Arctic Expedition, 1913-18 
middle of the inner margin. Unguiciilus represented only by a toothlike rudi- 
ment. Tenent hair single, unknobbed. Rami of tenaculum quadridentate. 
Furcula very long, extending as far as the first pair of legs, clearly appended to 
the fourth abdominal segment. Manubrium short. Dentes long, strongly 
bowed outward, apically convergent, with an obsolete transverse suture two- 
fifths from the base, and with the tubercles of the distal third arranged in trans- 
verse rings. Mucrones (figs. 2, 3) three-fifths as long as hind ungues, with outer 
and inner lamellae, and with a prominent dorsal rounded-triangular basal lobe. 
Anal spines absent. Body clothing of few minute curving setae; dens with 12 
to 17 long curving dorsal setae, most of which are in two longitudinal series. 
Integument tuberculate. Length, 1.3 mm. 
Podura aquatica, one of the most abundant collembolans in Europe and 
North America, occurs on the surface of standing water on the. margins of ponds 
and streams, having special structural adaptations for a semi-aquatic life. It 
swarms on vegetation or rubbish along the shore, and at times is blown against 
the shore in masses of enormous numbers. This species often appears in fresh- 
water aquaria, and is essentially a fresh-water species, though it has been found 
occasionally in pools of brackish water on the seashore. 
The species has been recorded from Siberia. From Canada, I have speci- 
mens taken at Arnprior, Ont., May 19, 1917, by Mr. Charles Macnamara. 
Great numbers on ponds, Demarcation point, Alaska, May 16, 1914; 
abundant, large and small, at Bernard harbour. Dolphin and Union strait, 
Northwest Territories, June 25, 1915. F. Johansen. 
Achorutes tullbergi Schaffer. 
Plate 1, fig.s. 4-10; plate 2, fig. 11. 
Achorutes duhius Tullberg, 1876.— Uzel, 1890.— Schott, 1894.— Dalla Torre, 
1895.— Schaffer, 1896.— Skorikow, 1900. 
Achorutes duhius, var. concolor Carpenter, 1900. 
Achorutes tullhergi Schaffer, 1900a. 
Achorutes tullhergi, var. concolor Schaffer, 1900a. — Wahlgren, 1907. — 
Folsom, 1916. 
Pigmented with irregular patches of dark blue pigment (typical form) or 
uniformly pigmented (var. concolor). Eyes (fig. 4) eight on each side. Postan- 
tennal organs (fig. 4) with four (sometimes five) peripheral tubercles. Antennae 
shorter than the head, with segments as 6:7:9:9 in relative lengths. Sense organ 
of third antennal segment as in fig. 5. Ungues (fig. 6) stout, slightly curving; 
inner margin unidentate one third from apex. Unguiculi with setaceously 
prolonged outer margin and with the basal lamella suboblong on the second and 
third pairs of feet. Tenent hairs knobbed; 2,3,3, as a rule; occasionally 3,3,3. 
or 1,3,3. Mucrones (figs. 7-9) one-third dentes in length, apically rounded, with 
narrow outer lamella. Rami of tenaculum quadridentate. Anal spines (figs. 
10, 11) two, half as long as hind ungues, arcuate, on prominent contiguous 
papillae. Clothing- of sparse short curving setae, with longer setae on the 
posterior part of the abdomen. Length, 2 mm. 
The specimens collected by the Expedition belong to the variety concolor 
Carp., which has been taken hitherto in Franz Jcsef Land, EUesmere land, 
Bohemia and Massachusetts. The typical form of the species has been reported 
from Nova Zembla, Spitzbergen and Siberia. 
Several specimens on ponds and from rotten driftwood, Bernard harbour, 
Northwest Territories, May, 25, 1916, June 18, 19, 1915; also several under 
driftwood, Demarcation point, Alaska, May 16, 1914. F. Johansen. 
