List of Crustacea Cladocera from Madisow, Wis. 395 
one or two specimens. At the time named I found in Lake Wingra, in 
water filled with Millefolium , immense numbers of the species in both 
sexes. Thousands were collected in a single haul of the cone-dredge. 
After about a week they disappeared and repeated efforts to find them 
in the same locality failed. Doubtless the winter eggs had been laid and 
both sexes were dead. It will be interesting to observe at what date the 
species will appear in 1892. 
The male measures about .36 mm in length and .24 mm in height. It 
has the same general form as the female. The first foot has a stout 
hook. The post-abdomen resembles that of the female, and is provided 
with numerous scattered hairs. The vas deferens opens above the ter¬ 
minal claws. The terminal claws are smooth in both sexes, differing 
from D. crassa in which they are denticulate. 
Species 47. Pleuroxus trigonellus, O. F. Mueller. 
This species is by no means abundant here, and is usually found in 
deep water, down to 12-15 feet. 
Species 48. Pleuroxus denticulatus, Birge. Plate XIII. Fig. 21. 
This is the ordinary Pleuroxus here. It corresponds to P. aduncus, Jur. 
in Europe. I give a figure of the male post-abdomen. 
Herrick remarks on the similarity of this species to P. procurvatus , . 
and suggests that the two names may really belong to varieties of the 
same species. I have looked carefully for connecting forms but have 
been unable to find then. 
Species 49. Pleuroxus gracilis, Hudendorff, var. unidens, Birge. 
I was not acquainted with Hudendorff’s paper when I wrote my de¬ 
scription of this species in 1877. Matile* notes the resemblance of the 
two forms and correctly points out that the chief difference lies in the 
overhanging projection of the upper posteal angle in P. unidens. As I 
find this difference constant and as there are other less important differ¬ 
ences, I retain my name as characterizing a variety. Both Hudendorff 
and Matile note the species as rare. I did the same in my former paper, 
having then found only about 15 specimens. By the use of the cone- 
dredge I have found it quite abundant in Lake Wingra in late summer 
and autumn. There is no difficulty in getting 25 to 100 specimens from 
one haul of the dredge. 
Species 60-62. Camptocercus. 
Three species of Camptocercus are found in Wisconsin. C. macrurus, 
O. F. M. has been formed in only a few specimens. 
I am doubtful whether Schoedler’s two species C. biserratus and C. 
rectirostris are really distinct. I find forms agreeing with both descriptions 
* Die Cladoceren der Umg. von Moskau, 1890, p. 37. 
