26 G Canadian Arctic Expedition, 1913-1918 



mandibular palp is thrown off, and the use of the second pair of antennae as 

 swimming instrument is discarded. . Apparently both sexes occur there in equal 

 numbers, the males attaining the largest size. As the sunmer passes their 

 numbers decrease, and their size seems to depend upon the length of time the 

 ponds they occur in carry any water. 



I have examined a great number of specimens of this species froin Green- 

 land and arctic Eurasia, found in the museums in London and Scandinavia. 



Genus ARTEMIOPSIS Sars. 



Artemiopsis stefanssoni. 



Artemiopsis Stefanssoni Johansen, (Preliminary diagnosis in Canadian Field- 

 Naturalist, vol. XXXV, No. 2, p. 29, issued June 22, 1921). 



This species was secured in one of the three large tundra ponds situated at 

 about 100 feet elevation on one of the gravel ridges near the coast of Bernard 

 harbour, south of our winter house. I collected a number of mature males and 

 females here, on October 6, 1915, by cutting a hole in the ice of the pond. 



Immature Stages 



On July 3, 1916,1 secured, in the same pond, fourteen larvae presumably of 

 the same species, measuring from two to three mm. in length. They were in the 

 metanauplius and post-mentanauplius stage, the youngest of them having large 

 second pair of antennae, and the abdomen (tail) not fully developed, though 

 both the paired eyes, and 10 to 11 pairs of foliaceous legs were present. In the 

 largest specimens the second pair of antennae were comparatively shorter, 

 and all the nine joints of the tail (abdomen) to be seen. As even the mature 

 specimens of the genus can hardly be distinguished from the genus Branchinecta, 

 except in the sexual characters, it follows, that the larvae are practically of the 

 same appearance as B. paludosa of corresponding age, so I do not find it necessary 

 to figure them. From B. paludosa of the same size they are distinguished by 

 having more of the adult characters (foliaceous legs developed, second pair of 

 antennae shorter, etc.) . The tail (abdomen) even when it has all its nine segments, 

 is shorter and more solid-clumsy than tapering, with the cercopods (each of 

 which ends in a long spine) less differentiated, as described under the adults. 



They were found in numbers among the stones covered by detritus-mud 

 and vegetation in the shallow bights of the pond, showing up by their pink or 

 pale rose colour. They were rather sluggish in behaviour and fairly easy to catch 

 by stirring up the water, which later that day (3.30 p.m.) had a temperature of 

 55° F. (Air 50° F., clear and warm). 



Branchinecta paludosa was not observed in these three ponds (though both 

 Lepidurus arcticus and other Entomostraca were common there (see p. 8), 

 during our stay at Bernard harbour. At this time of the year B. paludosa at 

 this locality had already reached such a size (1-1| cm.) that the two sexes could 

 be easily separated, thus five times the length of the Artemiopsis larvae. When 

 it is further remembered (see above and below), that the full grown Artemiopsis 

 were secured the preceding fall in this same pond, there can be little doubt but 

 that these larvae belong to the genus Artemiopsis, and not to Branchinecta. 



Description of Adults 



I give some illustrations (text figures 5-6) of the adults of this new and 

 interesting species, which shows certain differences from the only other species 

 hitherto known, A. bungei Sars, from eastern Siberia, sufficiently characteristic 

 to support a new specific name. The males (text-figure 5) measured from 7 

 to 10 mm., and in spite of their small size they were fully mature, and continually 

 copulating with the females. They had the eleven pairs of foliaceous legs, and 



