90 



The Canadian Field-Naturalist. 



Vol. XXXV. 



clam-shrimps, cladocera, ostracods and 

 copepods occurred in great numbers. The 

 Limneiis were conspicuous by theirorange 

 colour, and both sexes were seen, often in 

 copulation ; some of the females had al- 

 ready (May 16) their olive-coloured eggs 

 shining through the shell. The pools in 

 which they occurred I found to be the 

 deeper holes left in the bed of the ditch - 

 canal, much overgrown Avith water-plants, 

 and with many dead leaves in the bottom 

 from the large oak-trees scattered over tlie 

 pasture. 



The place was visited repeatedly, and all 

 during May the clam-shrimps were found 

 in the larger ponds not yet dried up com- 

 pletely. After a time the red colour of the 

 full-groAvn individuals changes from oran- 

 ge to brownish, and the egg-bearing fema- 

 les seem to be more numerous than the 

 males, the latter probably dying off rapidly 

 when their function is finished. The two 

 sexes were often seen in copulation, during 

 which process they seem unable to float 

 in the water, but are crawling over, the bot- 

 tom-mud or lying there. By keeping them 

 in a glass of water I observed how during 

 the act the female eventually closes its 

 shell, and the male has all it can do to 

 keep them both free of the bottom. It is a 

 very funny sight: the male moving all its 

 feet vigorously, trying to rise in the water, 

 but the female having the effect of a sinker 

 attached to him, so that the net result is to 

 cause them bot^ to roll over, wrestler- 

 fashion, owing to the globular shape of the 

 body. Sometimes two males would attack 

 one female, but probably this was because 

 so many were crowded together in the 

 bottle. 



From June on their numbers decreased 

 markedly; and at the end of the month 

 none Avere found (the last ones were se- 

 cured on June 19, Avhen the two .sexes were 

 still observed in copulation. Several of 

 these, the last survivors, had a growth of 

 minute, green Algae, etc., upon their shells, 

 a sign of decay). Around Ottawa their life 

 thus seems to last two months. It will be 

 seen, however, from the record ' of these 

 clam-shrimps from Saskatchewan, given 

 below, that where suitable surroundings 

 are found they may occur also later in the 

 summer. 



The weather during April, May and 

 June. 1921. around Ottawa, was very 



Avarm, and Avith practically no rain; it Avas- 

 interesting to observe, that Avhen a period 

 of unusualh^ hot Aveather arrived in the 

 first half of May, the faivA'-shrimps {En- 

 hranchipus gelidus) Avere not to be found 

 any more. I ascertained this by visiting 

 the various pools in which I had found them 

 so common only a fcAv Aveeks before. 



About one dozen specimens from a Avater- 

 hole on the margin of a Avood at Scarbo- 

 rough Junction near Toronto, Ontario, 

 June, 1908, A. G. Huntsman coll. (see 

 Natural History of Toronto Region, 1913. 

 p. 275). 



Three specimens from pond at Estevan,. 

 Sask., August 3, 1916, W. R. Quinn, coll. 

 (sent me from Royal Ontario Museum). 



Four specimens, the tAvo largest of which: 

 were egg-bearing females, from a slough 

 three miles north-east of Medecine Hat, 

 Alta., June 11, 1920, A. G. Huntsman coll. 

 They occurred together Avith Estheria cald- 

 welli, Streptocephalus coloradensis and 

 Lepidurus co uesii. 



One full-groAvn and three young speci- 

 mens from a shallow slough at WetaskiAvin 

 (near Edmonton), Alta., June 1, 1920, A. 

 G. Huntsman coll. The fairy-shrimp Eu- 

 hranchipus gelidus Avas collected in the 

 same slough. 



It thus seems as if this species is not 

 found in the Rocky Mountains, nor west of 

 them. It lias not been recorded from Alas- 

 ka, nor did I find it along the arctic coast 

 of this continent west of Bathurst Inlet 

 (Canadian Arctic Expedition). 



In size this species does not exceed half 

 a centimeter in length, tlie females gen- 

 erally being the largest. 



Another species {L. brachyujus) is 

 knoAvn from Scandinavia, Central Europe, 

 Russia and Siberia, and is AA^ell described 

 and figured by Sars (1896) p. 117, plates 

 18-20. He mentions particularly how he 

 only succeeded in finding it in one ditch 

 Avitli much vegetation in Finmark, in 

 August, though he examined carefully 

 many others; he also observed hoAv it 

 swims Avith the shell-valves Avide open, but 

 often sinks to the bottom; and. how the 

 males firmly grab the valves of tlie females 

 below by their "hands" for the purpose of 

 copulation. Some of the larval stages are 

 desci'il)ed by Grube. 



To the second family of clam-shrimps be- 

 long two genci'a, TAmnadia and Eidimna- 



