Similarity of Wisconsin and European Forms. 287 
Wisconsin. Europe. 
Moina affinis , Birge. 
Ceriodaphnia lacustris, Birge. 
Ceriodaphnia consors, Birge. 
Daphnia minnehaha , Herrick. 
Bunops scutifrons, Birge. 
Aona lepida, Birge. 
Pleuroxus denticulatus , Birge. 
Anchistropus minor, Birge. 
Chydorus rugulosus , Forbes. 
3/. rectirostris , Jur. 
(7. hamata , Lillj. 
(7. laticaudata, P. E. M. 
H. dentata, Matile. 
A. ( Maerothrix ) serricaudata y 
Daday. 
A elegans, Kurz. 
Z\ aduncus, Jur. 
A emarginatus, Sars, 
(7. gib bus, Lillj. 
Besides these, llyocryptus longiremis , Sars, is close to Z agilis, 
Kurz; Latonopsis occidentalis, Birge, is closely allied with Sars’ 
Z. australis from Australia. The genus has not as yet been 
found in Europe. 
Pleuroxus procurvatus, Birge, and Chydorus faviformis, Birge y 
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 Z>. retrocurva, are the representatives in this coun¬ 
try of the European Z. 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. 
Jcerusses, 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 t’ne- 
ii—4 
