ENTOMOSTRACA 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 an ten nee 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 Jf. paradoxa, 



*Moina rectirostris Juriue. 



Plates XXXIX, Figs. 1-4; XLI, Figs. 2, 5, 8, 10, 11. 



Juriue '20 (Monoculus rectirostris); Fischer '49 (Daphnia rectirostris); Leydig '60 

 (Daphnia rectirostris); Baird '50; Fric '72^ (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 M. brachiata 

 has two in a vertical position. The post-abdomen has twelve to 

 fourteen teeth as against nine or ten for 31. brachiata. The free caudal 

 margin of the abdomen is hairy. The shell margins below are armed 

 with distant and short teeth. Hellich thinks Kurz idefitified this 

 species with the last. With the above this species agrees in the form 

 of the head and antennae 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 si^ecific charac- 

 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 0.37 mm., depth of head 

 0.40. Head slightly angled above the eye; antennules short (not much 



