64 TWELFTH ANNUAL REPORT. 



men is more slender and has fewer teeth ; the differences are, how- 

 ever, hardly specific. 



I am not convinced that either D. cederstromii, Schoedler, or D. 

 retrocurva, Forbes, are really distinct species, although the latter, 

 with its more strongly crested head, is said also to have a series of 

 teeth on the terminal claw. Perhaps it forms with D. cederstro- 

 mii the fifth and extreme phase of this group. 



Since writing the above account of Daphnia kalbergensis this 

 truly monstrous species has come to light in the vicinity of Min- 

 neapolis. The opportunity is thus afforded to verify the suspicion 

 expressed above that a number of species must be united under this 

 name. P. E. Mueller gives the following measurements for U. kal- 

 bergensis: head 0.9 — 1.0mm., body 1.0 — 1.1mm., spineO.7 — 0.75mm. 

 Kurz for his D. vitrea gives a length of 0.85 mm. plus 0.25 mm., the 

 length of the spine. Judging from his figure, the head would not 

 measure over 0.35 mm. 



Forbes says of his D. retrocurva that the head is two thirds as 

 long as the body. 



Our specimens measured as follows: 



No. 1. 1.6 mm, head somewhat more than half the body and al- 

 most exactly like D. vitrea in form. 



No. 2. Head 0.6 mm., body 0.9 mm., spine 0.5 mm.; about 9 anal 

 spines. Head in this case moderately curved upward. 



No. 3. Head 0.95 mm., body 0.95 or less, spine 0.5 mm.; or the 

 head as long as or, indeed, considerably longer than the body and 

 directed upward. 



The males have the crest much lower, the spine longer, and the 

 form of antennules figured by P. E. Mueller. In the older females 

 the beak is elevated above the antennules, as remarked by Forbes, 

 but in smaller individuals there is very little difference between 

 our specimens and Mueller's figures. 



The claws of the post-abdomen have, besides the row of fine teeth 

 mentioned by Mueller, a cluster of sharp teeth just at the basa. 



Found, together with typical D. galeata and the rounded form, in 

 a small deep lake or expansion of a creek not far from Medicine 

 lake, Hennepin county, Minn. 



Sp. 5. Daphnia magniceps, (Sp. n) 



(Plate U. Fig. 15). 

 The peculiar form figured in the Tenth annual of this survey 

 seems indubitably new and is distinguished by the peculiar shovel- 

 shaped head, which is scarcely crested but is broadest beyond the 



