8 A Canadian Arctic Expedition, 1913-18 
As Linnaniemi ('12, p. 102) has shown, the original descriptions of Tetra- 
canthella pilosa by Schott were based upon two distinct species; now known 
respectively as pilosa and ivahlgreni. The specimens that I have studied agree 
accurately with 4he description and figures given by Linnaniemi of the latter 
species. 
He says that in Finland T. wahlgreni liv^s under moss and lichens, as well 
as under stones, on the rocky summits of the mountains, where it may almost 
always be found, not infrequently in considerable numbers. Sometimes it can 
be taken also on the surfaces of pools of water. It has made its appearance 
early in summer, before the snows have melted on the mountain tops. Common 
as the species is on the summits of the mountains, it is seldom found in the 
timber region, but oftener, however, in the subalpine zone. 
T. ivahlgreni has been reported from Norway, Sweden, Finland (north of 
the Arctic circle), Spitzbergen and Bear island, and is essentially Arctic in its 
distribution. 
Four specimens (one spoiled by dissection), on the surface of a pond in a 
swamp, Bernard harbour. Northwest Territories, June 18, 1915. F. Johansen. 
Folsomia quadrioculata (Tullberg). 
Plate 5, figs. 42-47. 
Isotoma quadrioculata Tullberg, 1871, 1872, 1876.— Stuxberg, 1887.— Uzel, 
1890.— MacGillivrav, 1891, 1896.— Moniez, 1891.— Schott, 1894, 1902.— Dalla 
Torre, 1895.— Renter, 1895.— Lie-Pettersen, 1896, 1898, 1907.— Meihert, 
1896.— Schaffer, 1896, 1900a, 1900b.— Poppe and Schaffer, 1897.— Lubbock, 
1898.— Scherbakov, 1898a, 1898b.— Carl, 1899, 1901.— Wahlgren, 1899b, 1900a, 
1900b, 1906a, 1906b.— Absolon, 1900.— Skorikow, 1900.— Borner, 1901a.— 
Krausbauer, 1902.— Agren, 1903, 1905.— Guthrie, 1903.— Axelson, 1904, 1905b, 
1906.— Evans, 1908. 
Isotojua {Folsomia) quadrioculata Axelson, 1905a. 
Folsomia quadrioculata (Axelson) Linnaniemi, 1907, 1909, 1911, 1912. — 
Collinge and Shoebotham, 1910. 
Dull grey to greyish black, pigmented with blackish spots of irregular form, 
size and distribution. Small specimens may be white, or white with scattered 
spots of greyish blue. Large specimens are often blackish, mottled with white, 
or unpigmented, spots; pale across the intersegmental regions and ventrally; 
with antennae, legs and manubrium pigmented, and dentes unpigmented. Eyes 
2 + 2 (fig. 42), one behind the other, each with its separate pigment spot, the 
posterior eye being the smaller. Postantennal organs (fig. 42) long, narrow, 
with parallel sides, feebly curving. Antennae varying from a little shorter to a 
little longer than the head; second segment a little longer than the third; fourth 
segment two to three times as long as the first. Sense organ of third antennal 
segment as in fig. 43. Fourth antennal segment with slender curving sensory 
setae, much like the other setae. Body stout. Fourth, fifth, and sixth abdominal 
segments ankylosed; with a trace of a dorsal suture between the fourth and 
fifth segments. Anus ventro-caudal. Unguis (fig. 44) stout, curving, simple, 
without teeth. Unguiculus small, extending a little less than half as far as the 
unguis, lanceolate, pointed, untoothed. Tenent hairs absent. Furcula append- 
ed to the fourth abdominal segment, short, extending almost to the posterior 
margin of the second abdominal segment. Manubrium (fig. 45) with two pairs 
of ventro-apical chitinous hooks between the bases of the dentes. Dentes (fig. 
46) stout, slightly tapering, with a few crenulations near the middle of the dorsal 
region. Mucrones (fig. 46) bidentate; apical tooth hooked; antcapical tooth 
usually larger than the other, erect or curving slightly forward. Rami of 
tenaculum quadridentate; corpus with a single stout curving seta. Clothing 
of simple setie (fig. 47) of three kinds: (1) moderately long stiff dense setae, 
