Febniaiy, 1921.] 



The Canadl\n Field-Naturalist. 



25 



The males of the two Poly art emklla 

 species are easily distinguished by their 

 elaspers. lu one {P. hazeui Murdoch) the 

 claspers are big, antler-like processes with 

 four branches : in the other (P. judayi, De 

 Dees), they are more like fish-hooks (or 

 sickles) and three branched, thus more like 

 those of Polyartemia. 



The first named species, about 1 cm. long, 

 was originally discovered by Murdodi of 

 the International Polar Expedition in 

 tundra pools at Point Barrow, Alaska, in 

 the middle of Juh% 1882, and described and 

 figured by him in the reports of the said 

 expedition p. 150. A better description 

 and figure of it has later been given by De 

 Dees, p. 106-07, (1910) ; according to 

 Pearse * it also occurs at other places along 

 the arctic coasts of Alaska and Yukon Ter- 

 ritory. It has hitherto not been found east 

 of the Mackenzie River. During the Can- 

 adian Arctic Expedition I secured in tundra 

 l)onds at Teller (Port Clarence), Alaska, 

 a couple of males and half a dozen females 

 of apparently the same species in the be- 

 ginning of August, 1913. They differ in 

 various points from Murdoch's descrip- 

 tion, but a full account and figures of them 

 wall be given in the reports of the Can- 

 adian Arctic Expedition (Vol. VII, Part 

 G.) to which I refer. 



Poly art emiella judayi (about 12 mm.) 

 was originally described by De Dees in Aii- 

 vales des Sciences Naturelles, Paris, 9th 

 series. Vol. XI, 1910, p. 108-11, from spe- 

 cimens collected by Dr. Juday on the Pri- 

 bilof Islands in Bering Sea. I did not 

 myself find this species in Alaska, and as 

 is the ease with the other species (P. ha- 

 zeni) little is known about the life history, 

 the young stages not having been secured 

 as yet, though both sexes are known. '" 



The genus Poly art emiella thus seems to 

 be limited to the arctic and subarctic parts 

 of northwest America, west of Mackenzie 

 River. 



To the second group of fairy-shrimps 

 (those with 11 pairs of foliaceous legs) 



4 Polyartemiella hanseni (Murdoch) coll. by 

 J. M. Jessup at Muskeg Lake, lat. 69 40' N., 

 long. 141 W., July 25, 1912, and at Muskeg 

 pools on flood plain of Firth River, lat. 69 20' 

 N., long. 141 W., June 23, 1912 (Pearse, 

 1913). 



s The females are a few millimeters longer 

 than the males. 



belong three or four families, of W'hich 

 only two have been recorded from Canada 

 and one of these latter also from Alaska. 

 The characters separating the families are 

 not very good, because tjjaey are mainly the 

 appendages (claspefs and accessories) on 

 the head of the ripe males, and even two 

 species belonging to the same genus are ex- 

 tremely different in this respect. I, there- 

 fore, do not find it necessary to give the 

 distinctions between tlie families here, be- 

 yond mentioning, tliat the genus Thamno- 

 cephalus, which occurs in the middle parts 

 of the United States (Kansas, Colorado, 

 etc.), is very distinct from all the other 

 fairy-shrimps belonging to this group, b}' 

 reason of the fusion of the post-genital 

 segments and the cereopods. 



Probably the most widely distributed of 

 all fairy-shrimps is the circumpolar form 

 Branch inecta paludosa O, F. Miiller. It 

 reaches a length of 2 cm., and the male 

 claspers are fairly simple (though when 

 the animals are ripe, well developed), con- 

 sisting of a stout and long, cylindrical 

 basal part with a row of short spines on 

 their inner margin, and when fully deve- 

 loped, a little longer, more slender, triang- 

 ular and falciform, apical part (joint). 

 The protruding parts of the male genita- 

 lia are thick, arcuated and paired (bifid), 

 while the ovisac of the female is very long, 

 slender and thickest near its free rounded 

 end. 



This species was first described by Otto 

 Fabricius from West Greenland as Cancer 

 stagnalis (Fauna Groenlandica, p. 247,^ 

 1780), and much confusion was caused by 

 his thinking it was the same as Linnaeus' 

 species of the same name from Europe, and 

 by 0. F. Miiller in his Zoologia Danica II, 

 calling it Cancer paludosus, in the belief 

 that it Avas the same genus as the species 

 {Branchipus stagnalis), occurring upon the 

 continent of Europe and first recorded b}' 

 Linnaeus as Cancer stagnalis. It was 

 finally established as being the circumpo- 

 lar, arctic form Branchinecta paludosa by 

 Verrill. It is distributed from Alaska to 

 Greenland in the new world, and in Eura- 

 sia it has been recorded from northern 

 Scandinavia, Spitsbergen, Novaja Semlja 

 and Siberia. Curiously enough it has not 

 yet been found in East Greenland. Another 

 species (B. gainii) of the same genus was 

 found by Charcot in the Antarctic. 



