ENTOMOSTRACA OF MINNESOTA. 203 
Daphnia cucullata Sars. 
Kurz (vitrea). 
Very like the above, but the margin of head is not straight below, 
is, however, extremely variable and ends in a sharp angle. The eye 
lies nearly midway between the heart and the end of the head and 
near the lower margin. The two anterior processes of the abdomen 
are united for most of their length. Anal teeth five toseven. Claw 
ciliate. The flagellum of the male antenna is about as long as the ter- 
minal sete. 
D. apicata Kurz seems to be a large variety lacking the sharp spine: 
of the head. In the main it agrees quite well. Although the post- 
abdomen is broader than figured by Mueller, the number of teeth cor~ 
responds with Sars’ description. 
Length 0.95 to 1.11 mm. 
* Daphnia kalbergensis Schoedler. 
PLATES XXVII, Fias. 1-3; LIII Fias. 5-8. 
Schoedler (ccederstroemii, and berolinensis); Forbes (retrocurva). 
Rather delicate species of moderate size, inhabitants of clear and 
deep waters. Form oval, with a long nearly straight spine springing 
from near the middle of the posterior margin. Head very large and 
produced into an enormous helmet-like crest, which projects cepha- 
lad and may be somewhat or greatly curved dorsad. The size of the 
crest and its form are very variable even iu the same gathering. Eye 
small, with few lenses, distant from the ventral margin, macula want- 
ing. Antenne weak. Post-abdomen narrow, with from six to twelve 
anal teeth; claws weakly ciliated. Abdominal processes discrete. 
As above stated, the close association of forms in the same gather- 
ing ranging from D. vitrea to the extreme of D. retrocurva seems to: 
forbid their separation, even varietally. The case of D. vitrea is most 
open to doubt. The chief differences seem to lie in the small number 
(4) of anal teeth and the fusion of the two anal processes. A young 
specimen from Lake Minnetonka had but four large teeth and two 
inconspicuous ones and the anal processes were less distinct than in 
older individuals. All transitions could be-found. We agree with 
Hellich that this, at most, is a depauperate variety of D. kalbergensis. 
There seems to be absolutely no good reason for separating D. ceder- 
stremit or D. retrocurva, as the differences are largely a matter of uge 
and freedom to develop typically. 
P. E. Mueller gives the following measurements for D. kalbergensis: 
Head 0.9 to 1.0 mm., body 1.0 to 1.1 mm., spine 0.7 to 0.75 mm. 
