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 sjDinules on the claw and a larger number of anal 

 spines — 18 to 20. Daday figures claws such as Birge describes. 



* Daphiiia pulex var. uasutus Herrick. 

 Plate XXXV, Figs. 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 si)ines 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. 



*Daphiiia pulex var. pulicaria Forbes. 



This seems to closely resemble the type. The fact that the antennse 

 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 

 antennse of the female.) 



[Dapliiiia peunata Sars] 



"Antecedenti [D. pulex) simillima, caput autem a latere visum latius, rostro bre- 

 -viore, supra visum testa cetera parum angustius fere coidiforme, antice acuminatum. 

 Processus anteriores duo di.«juncti. Margo posterior postabdominis in medio sinulo 

 parvo et infra hunc utrinque aculeis 16-18 armatus. Color ut in antecedente. Longit 

 ■0.2^ 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 curvirostri.s Elymann.] 



The differences relied on to distinguish this species from P. 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. 



