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 wdhlgreni. The specimens that 'I have studied agree 

 accurately with the 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. wahlgreni 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.— MacGillivray, 1891, 1896.— Moniez, 1891.— Schott, 1894, 1902.— Dalla 

 Torre, 1895.— Renter, 1895.— Lie-Pettersen, 1896, 1898, 1907.— Meinert, 

 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. 



Isotoma (Folsomia) quadrioculata Axelson, 1905a. 



Folsomia quadrioculata (Axelson) Linnaniemi, 1907, 1909, 1911, 1912. — 

 ColHnge 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 ventfally; 

 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 

 setse, 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; anteapical 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 setae (fig. 47) of three kinds: (1) moderately long stiff dense setae, 



