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194 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
* Daphnia pulex var. denticulata Birge. 
The lower margin of the head is said to be less convex [concave?] 
than D. pulex. The abdominal processes are less hairy, there is a 
continuous series of spinules on the claw and a larger number of anal 
‘Spines—18 to 20. Daday figures claws such as Birge describes. 
* Daphnia pulex var. nasutus Herrick. 
PLATE XXXYV, Fies. 1-4. 
This in some respects is more like the type. It has an elongate 
‘oval form with spine of variable length arising from above the middle. 
The impression between head and body is slight. The ventral margin 
-of the head is concave and the beak is curved caudad. The terminal 
claw of the post-abdomen is furnished with two combs of fine teeth. 
‘The anal spines are 10 to 14. The abdominal processes are hairy. 
Neither this variety nor the above seems to possess the two teeth on 
the front margin of the claw. 
* Daphnia pulex var. pulicaria Forbes. 
This seems to closely resemble the type. The fact that the antennz 
are ornamented with spines rather than scales is noticed, The first 
abdominal process is smooth, as it is also stated to be in the European 
form by some authors. The male is said to differ more, but compari- 
son of Forbes’ figure with that of Elymann reveals nothing of impor- 
tance. (Elymann figures spines rather than scales on the base of the 
-antennee of the female. ) 
[Daphnia pennata Sars. ] 
‘‘Antecedenti (D. pulex) simillima, caput autem a latere visum latius, rostro bre- 
viore, supra visum testa cetera parum angustius fere cordiforme, antice acuminatum. 
Processus anteriores duo disjuncti. Margo posterior postabdominis in medio sinulo 
parvo et infra hunc utrinque aculeis 16-18 armatus. Color ut in antecedente. Longit 
0.24 mm.”’ 
Although admittedly very close to D. pulex, it is said to differ in 
the broad depressed head, which is uniformly rounded in front and 
deeply excavated in front of the beak, which is short and deflected. 
The post-abdomen has 16 to 18 teeth. The antennules of the male are 
almost as long as the head, bearing a long pointed flagellum and a 
short lateral seta. 
[Daphnia curvirostris Elymann. | 
The differences relied on to distinguish this species from D. pulex 
seem to us quite inadequate. The head is more depressed and this 
gives to it a quite different appearance. The male antennule is thick- ; 
ened slightly at the middle and the flagellum is longer. The hairy ; 
abdominal process is absent. 
