ENTOMOSTRAUA OF MINNESOTA. 163 
The description given by Hellich is the most full at our disposal 
and runs about as follows: Body robust, untransparent greenish in 
color. The head depressed and broadly and deeply excavated above 
the eye. Lower angle of head with the front strongly arched. Eyes 
with many lenses; pigment fleck absent. Antennules springing from 
the middle of the lower margin of the head, slightly enlarged at the 
middle, covered with short hairs, with one lateral flagellum, as long 
as the head. The antenne reflexed do not attain the posterior margin 
of the shell and are hairy. Shell margin short-spined in front and 
armed with fine spines to the posterior lower angle. Shell faintly 
reticulate. Post abdomen large, lateral spines ten to eleven, the first 
being bifid. Claws strongly curved, with a series of eight or nine strong 
teeth at the base and a continuous series inwardly. Length 1.3 to 1.4 
mm. Male smaller, head extended. Antennules affixed nearer the 
front, longer than the head, flexed at the middle, armed at the end 
with four cleft’ claws and at the middle externally with three short 
bristles. Unfortunately Hellich does not describe the first foot of the 
male, though P. E. Mueller figures it as devoid of the elongate flagel- 
lum characteristic of M. paradoxa. 
*Moina rectirostris Jurine. 
PLATES XX XIX, Fies. 1-4; XLI, Fras. 2, 5, 8, 10, 11. 
Jurine ’20 (Monoculus rectirostris); Fischer ’49 (Daphnia rectirostris); Leydig ’60 
(Daphnia rectirostris); Baird ’50; Fric ’721 (Daphnia rectirostris); Kurz ’74; 
Weismann ’77; Hellich ’77; Schoedler ’77; Herrick ’84. 
From the preceding, which it too closely resembles, this species 
differs in the fact that the shell has no trace of reticular marking, the 
ephippium has but a single ova horizontally placed, while MZ. brachiata 
has two in a vertical position. The post-abdomen has twelve to 
fourteen teeth as against nine or ten for M. brachiata. The free caudal 
“margin of the abdomen is hairy. The shell margins below are armed 
with distant and short teeth. MHellich thinks Kurz identified this 
species with the last. With the above this species agrees in the form 
of the head and antenne and nearly all other characters. 
As for the American forms, it is quite possible that we shall event- 
ually be enabled to distinguish several varieties of the brachiata-recti- 
rostris type, but very careful study of local and seasonal influences will 
be necessary to give to such distinctions any value as specific charae- 
ters. That considerable variation does occur is beyond question. 
- We may recognize two types which do not correspond fully with the 
two European varieties. 
VARIETY A—Length 1.1 to 1.2 mm., head 0.87 mm., depth of head 
0.40. Head slightly angled above the eye; antennules short (not much 
11 
