Ceriodaphnia quadrangula—Daphnia pulex. 295 
Ceriodaphnia lacustris is perhaps most closely allied to C. ham- 
■ata , Sars (90, p. 36). That species has a similar form and habitat, 
but differs in the shape' of the fornices, which are produced “ in 
spinam procurvatam, hamiformem, sat prominentem. ” C. 
hamata also lacks the spines on the head. C. punctata , P. 
E. Mueller is also a pelagic species, and agrees with C. lacustris 
in the structure of the head and perhaps, in that of the post¬ 
abdomen. The antennules, however, are far longer in G. punc¬ 
tata , and the fornices are much smaller. C. pelagica 1 Imhof 
should also be a similar species but I have not been able to 
refer to Imhof’s description. 
Ceriodaphnia quadrangula, O. F. Mueller. 
Sars’ account of this species (’90, p. 36.) led me to look 
carefully over my material from northern Wisconsin with refer- 
ence^to it. I conclude that the species is present. I find how¬ 
ever, no really trustworthy figures of the species, and it is very 
difficult to identify it from the conflicting descriptions of vari¬ 
ous authors. Unquestionably more than one form has been de¬ 
scribed under this name. Ther'e is clearly a form without a 
pecten on the caudal claw and with no angle in front of the an- 
tennule, and another similar but with such an angle. I have 
•called the first form C. quadrangula and the second C. pul- 
chella , but am not sure of my identifications. 
Daphnia pulex, var. pulicaria, Forbes. 
Plate XII, Figs. 1, 2, 3, 4, 5. 
A pelagic species of Daphnia , found in several localities, 
seems to belong to this variety, described by Forbes (’93, p. 
242, pi. XXXVII, fig. 1). This species agrees in general with 
D. pulex , but is transparent and is found in the open water of 
of lakes and not in muddy pools. A species very close to it is 
present in temporary pools at Madison. This also differs in 
color from the typical D. pulex. Although dirty it lacks the 
yellow tint characteristic of the true D. pidex. In some lakes 
a species was found which seemed more closely allied to D. 
