204 GEOL. AND NAT, HIST. SURVEY OF MINNESOTA. 
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 
almost exactly like D. vitrea in form. 
No. 2. Head 0.6 mm., body 0.9 mm., spine 0.5 mm.; about nine 
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 speci- 
mens 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 base. 
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, Minnesota. 
We have since found this species at a depth of 80 feet in Lake Min- 
netonka, and here also in association with D. hyalina. The range of 
variation is exceedingly great as indicated by the figures of Plate 
LITT. 
Having given as fall a catalogue of the well known and accessible 
species as our circumstances now permit, it remains to notice the ex- 
istence of others which are either imperfectly described or the descrip- 
tions are out of reach. 
Daphnia similis Claus. 
PLATE XX XV, Bic. 5; LI, ia. 7: 
The description of this species, which was bred in confinement from 
eggs brought in mud from Jerusalem, I am, unfortunately, unable to 
quote. Judging, however, from the figures which alone I now have 
access to, it belongs in the group of D. longispina, though in many 
particulars it resembles D. schefferi. The form is elongate, the spine 
short and springing from the upper margin. The antennule of the 
female is very large and flagellate, while that of the male is like that 
of D. sche fferi. The flagellum and hook of the first foot of male are 
rather small. 
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