May, 1921.] 



The Canadian Field-Xaturalist. 



93 



dia. Tlie shell of the former genus (estab- 

 lished by Broig-nard in 1820) , is very broad- 

 ovate, flat and with a great number (18) 

 of lines of growth. So far only one species 

 has been found upon this continent, name- 

 ly L. americana, known from Massachu- 

 setts; it may therefore possibly occur also 

 in eastern Canada. Sars (1896) thinks it is 

 the same as L. lenticulons Linn, known 

 from Scandinavia and Central Europe; he 

 describes and figures this on p. 85, plates 

 14-16, and the larval stages on plate 17. 

 He says the females already carried the eggs 

 at the end of July and that the larvae 

 were found in the middle of the same 

 month ; he expresses the opinion, however, 

 that only one brood is developed each sum- 

 mer. The size of L. americana is about 

 1 cm. The other genus {EuUmnadia) is 

 represented upon this continent In' two 

 species of which one is known from Kan- 

 sas, Nebraska and Texas, and the otlier, E. 

 agassizii "' from Massachusetts and Ontario. 

 The genus has a narrow ovate, very trans- 

 parent shell with 4-5 lines of growth about 

 1-2 em. long. I have before me four speci- 

 mens of E. agassizii collected by A. G. 

 Huntsman in pools on rocks at Go Home 

 Bay (Georgian Bay) Ont., August 15th 

 (1905), sent me from the Royal Ontario 

 Museum (See Natural Hist or ij of Toronto 

 Region, 1913, Y). 215). 



Dr. Huntsman writes me (June 1920), 

 that "this species occurred at two places 

 at Go Home Bay, namely at Station Island 

 and at Split Rock Island. In each case a 

 large number of specimens was found in a 

 small, temporary pool in the rock, the pool 

 probably not being more than a foot or two 

 feet in diameter, and quite shallow. It 

 seemed extraordinary that so many indi- 

 viduals of relatively large size should occur 

 in so little water ..." 



The third family of clam-shrimps . (Es- 

 theriidae) is represented on this continent 

 by the genus Estheria of which more than 

 half a dozen species are known from the 

 United States, but only one, E. caldwelli 

 (Cyzicus mexica7ia) > from Canada. It is 

 interesting that no species of this genus has 

 so far been found east of Saskatchewan 



'' First described (and the genus established) 

 by Packard in 1874, from specimens collected 

 by W. Faxon in Massachusetts in 1873; the 

 females had then (August) yellowish eggs. 

 The following July-August the young ones were 

 I about 1 line in length. 



Tlie genus is 



and the Mississippi River, 

 easily recognized by the oval, more or less 

 globose shell oi an amber colour (thus 

 much like a clam-shell) showing about 20 

 lines of growth until about 1^ em. long. 

 I have before me five specimens of E. cald- 

 welli from a prairie-slough at Estevan, 

 Sask., collected by W. R. Quinn on August 

 6th, 1916, and sent me from the Royal 

 Ontario Museum. The species was first 

 described in 1862 by W. Baird from spe- 

 cimens collected by W. Caldwell in Lake 

 Winnipeg, and two years earlier by C. 

 Clans from Mexico ; it has fui-ther been 

 recorded from Kansas, Nebraska, Ken- 

 tucky, Ohio and New Mexico. 



I have recently received one more spe- 

 cimen collected by Dr. A. G. Huntsman on 

 June 11, 1920, in a slough three miles 

 north-east of Medicine Hat, Alta., where it 

 occurred together with Limnetis goiddii 

 and other Entomostraca. The specimen is- 

 about 9 mm. long, while some of the five 

 specimens from Estevan, Sask., mentioned 

 above were almost double this size.^ 



Clam-shrimps were recorded from Fin- 

 land by Linnaeus ; but the order was well- 

 described for the first time by Herman in 

 the beginning of the nineteeaith century. 

 Postscript. 

 In June, 1920, I received a letter from 

 Dr. Chancey Juday, of Madison, Wiscon- 

 sin, giving me some new records of clam- 

 shrimps collected by J. M. Jessup in May- 

 July, 1911 and in July. 1912, in Alaska 

 and Yukon Territory. 



As these are the first records of Con- 

 chostraca from the arctic and subarctic 

 parts of this continent, and the first time 

 the two species in question liave been found 

 in America,* it is of importance to have 

 them included in this article. The records 

 are: 



Lynceus hrachyurus {Limnetis h.) : 

 Lakes and bog-holes on OkLCrow River 

 flat about 40 miles north of New Rampart 

 House ; Lake 48 miles north of New Ram- 

 part House ; Morainal lakes, 30-35 miles 

 north of White Horse, Yukon Territory. 

 Limnadia lenticidaris : Lakes on coastal 



" The gen us -name Estheria was made by 

 Rueppell, in 1857, but later the genus was 

 found to be the same as Audouin's Cyzicus, 

 established in 1837. Similarly Baird's species 

 E. caldwelli, described in 1862, has been proved 

 to be the same as C. mexicanus, first des- 

 cribed by Claus two years previously.. 



