ENTOMOSTRAOA OF MINNESOTA. 193 



DaphDia sclioetlleri Sars. 

 Schoedler '58 (longispina) ; Sars '61; Hellich '77; Elymann '67; Daday '88. 



Head arched in front, ventral margin gently sinuous, beak acute, 

 projecting ventrad. Eye large, near the margin of the head. Body 

 oval, spine long. Post-abdomen of moderate size, with 12 [14 to 16] 

 anal teeth. Claw with comb of spines. Abdominal processes discrete 

 but approximate [Daday] or distant from each other [Elymann]. 



There is wide disagreement between the various descriptions of 

 this species. 



Daphnia brevi spina Daday. 



Daday '88. 



Head short, slightly projecting ventrad, front strongly rounded, 

 ventral margin somewhat sinuate. Beak short, acute, inclined ven- 

 trad. Eye distant from the frontal margin of the head. Shell oval, 

 with a slight depression between head and thorax, margins arcuate, 

 with a very short spine. No crest. Post-abdomen rather long with 

 delicate lateral setfe; anal teeth 12, curved, almost equal. Claw with 

 a comb of spines and a continuous series of fine setic. Abdominal 

 processes discrete, setose. Length 1.2 to l.S mm., height 0.75 to 

 1.2 mm. 



* Daphnia piilex De Geer. 



De Geer 1778; Hellich '77; Lutz '78 and '79; Elymann '86; Daday '88, Matile '90. 



Body large, stout and thick, rather opaque, reddish. Head broad, 

 depressed, front protuberant. A^entral margin of head deeply con- 

 cave. Beak acute, curved backward. Fornix high. Eye small, with 

 few lenses. Antennules short, conical, extending but little beyond 

 the beak. Antennse short, slender, evidently marked with scuta, 

 with long densely pectinate setse. The shell is not separated from the 

 head by a depression in mature females and is oval in outline. The 

 ventral margin is much more strongly arched than the dorsal. Si^ine 

 very short, straight, inclined upward and inserted above the middle 

 of the posterior margin. Shell margins with short spines. Surface 

 reticulate in fine quadrangles. Cteca short, clavate, curved dorsad. 

 The abdominal processes approximate; the first twice as long as the 

 second; the third small. Post-abdomen long, narrowed toward the 

 end. Its distal end is rounded. Anal teeth 12 to 14, nearly equal. 

 Claws curved, with two combs of teeth, the higher consisting of six to 

 seven teeth, the lower of three to four. Length of female 2.15 mm., 

 height 1.23 mm., spine 0.16 mm. It is at present impossible for the 

 writer to unravel the relations of the numerous varieties and supposed 

 species of the^)^^^; group. Probably most of them are simple syno- 

 nyms. The following American varieties may be mentioned: 



