March, 1921.] 



The Canadian Field-Naturalist. 



47 



As to its life-hLstory (development), t/ie 

 stages bet^\een the eggs and the adults 

 are unknown. 



The fourth Lepidurus species is the well- 

 known, circumpolar form {L. arcticus Pal- 

 las) {L. ylacialis Kroyer), first well des- 

 cribed from West Greenland, it is im- 

 mediately recognized by the fact that the 

 telson ends in a triangular (not spatulate) 

 plate obtusely pointed and with spiny 

 edges. Its distribution is very similar to 

 that of Branchinecta paludosa, having been 

 recorded from Greenland ^, Iceland, Spits- 

 bergen, Northern Scandinavia, Novaja 

 Semlja, Siberia and on this continent from 

 Alaska to Baffin Bay. Its southern limit 

 is not definitely established, but indicated 

 by the following records in North America, 

 Pribilof Islands, Teller, Point Barrow and 

 Martin Point, Alaska; south side of Dol- 

 phin and Union Strait, King William Land 

 and Labrador. Several of these records are 

 based upon my own collections made on 

 the Canadian Arctic Expedition, and the 

 species will be treated in detail in the re- 

 ports (Vol. VII, Part G) of that expedi- 

 tion. I have also given a detailed account 

 of its biology and development as I studied 

 it in Northeast Greenland (Meddel. om 

 Groenland, Yol. 45, p. 333-37). Its struct- 

 ure, etc., has been well described and beau- 

 tifully illustrated bv Sars (1896) p. 68- 

 82, fab. 11-13. Its life-history is now 

 fairly well known. The hibernating eggs 

 hatch in June, and the nauplius, which is 

 not unlike that of Branchinecta, soon as- 

 sumes the metanauplius stage (.see above). 

 It is rather sluggish and seems to venture 

 forth over the mud-bottom only when it 

 has grown considerably and assumed the 

 adult's color; even then it often takes re- 

 fuge under the larger individuals. I se- 

 cured the metanauplii in Greenland in 

 June, but the youngest individuals I found 

 during the Canadian Arctic Expedition 

 (taken on July 3, 1916, at Bernard Har- 

 bour, N. W. T.), were 3 mm. long, and 

 practically like the adults. Both in Green- 

 land and in the Canadian Arctic I first 



secured the few males in August, though 

 adult females together with younger ones 

 were secured from the end of July on ; the 

 latter first had ripe eggs in their brood- 

 pouch in August. The last Lepidurus in 

 the year were secured on October 6, 1915, 

 together with the new Branchipod men- 

 tioned p. 29 {Artemiopsis stefanssoni). 

 Even in the autumn and fall the ani- 

 mals range in size from about I/2 cm. to 2 

 cm., thus proving that they represent both 

 that and the preceding years' brood (gen- 

 eration). 



All the Apus species occurring on this 

 continent have so far been recorded only 

 from the middle and western parts of 

 United States, and none from Canada or 

 Alaska. One of them {A. lo7igicaudatus) 

 has, however, been recorded from Yellow- 

 stone River, so it is possible it ranges 

 across the boundary into Alberta. Of the 

 species occurring in Europe, some are in- 

 teresting because they have been known for 

 a much longer time than the American re- 

 presentatives. The genus was first des- 

 cribed in the first half of the 18th century, 

 and was subsequently listed by Linnaeus 

 under the name of Monoculus. The genus 

 Lcpidu)us was not separated out until more 

 than half a century later, by Schaeffer. 



A parasitic Trematode {Distomum apo- 

 dis Pack.) has been observed in the egg- 

 sacks of the genus Apus in North America 

 (see A. S. Packard, in Amer. Naturalist, 

 Vol. XVI, 1882, p. 142). 



G. 0. Sars in ''Crustacea" (2d. Norwe- 

 gian Arctic Expedition 1898-1902 

 ("Fram"), 1911, p. 15) records Lepidu- 

 rus apus (Lin.), from a freshwater-swamp 

 at Cape Rutherford, east side of Grinnell 

 Land (about lat. 79 N., long. 75 W.), 

 on August 29, 1898. * This is the first time 

 this species has been found in the arctic 

 regions, and in America. It is, I believe, 

 the same species as L. {Apus) productus 

 Bosc, known from a number of places in 

 Europe. 



(To be continued). 



s West coast up to Foulkefjord and Northum- 

 berland Island, east coast at least to 77 N. 



4 Lepidurus arcticus was also secured by this 

 expedition at Cape Rutherford. 



