Similarity of Wisconsin and European Forms. 287 



Wisconsin. Europe. 



Moina affinis, Birge. M. rectirostris, Jur. 



Ceriodaphnia lacustris, Birge. C. hamata, Lillj. 



Ceriodaphnia consors, Birge. C. laticaudata, P. E. M. 



Daphnia minnehaha, Herrick. D. dentata, Matile. 



Bunops scutifrons, Birge. B. (Mdcrothrix) serricaudata, 



Daday. 



Alona lepida, Birge. A. elegans, Kurz. 



Pleuroxus denticulatus, Birge. P. aduncus, Jur. 



Anchistropus minor, Birge. A. etnarginatus, Sars. 



Chydorus rugulosus, Forbes. C. gibbus, Lillj. 



Besides these, Ilyocryptus longiremis, Sars, is close to I. agilis, 

 Kurz ; Latonopsis occidentalis, Birge, is closely allied with Sars' 

 L. australis from Australia. The genus has not as yet been 

 found in Europe. 



Pleuroxus procurvatus, Birge, and Chydorus faviformis, Birge, 

 do not seem to be closely connected with any other known species. 



The forms of the genus Daphnia, described by Forbes under 

 the name of D. retrocurva, are the representatives in this coun- 

 try of the European D. cucullata with its varieties, especially 

 Kahlbergiensis, Schdl. Perhaps as all our forms are provided with 

 a pectinated caudal claw, it would be well to make of them a 

 separate species. This would then probably bear the name D. 

 kerusses, Cox. In any case the Wisconsin forms closely corre- 

 spond to those of Europe in nature and range of variation of 

 the crest of the head. 



It thus appears from the list and comments that the fauna of 

 Wisconsin differs very slightly from that of Europe. No genus 

 thus far discovered here is peculiar to America, and only two 

 of our species lack a close relative in Europe or some other widely 

 separated land. So close is the relation between our species and 

 their foreign allies that we cannot doubt that more careful 

 study of the range of variation shown by the Cladocera will re- 

 duce many of our thirteen peculiar species to the rank of vari- 

 eties. 



In a recent paper on the geographical distribution of the 

 ii— 4 



