178 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA, 



about the lower part. The smaller species are frequently deeply col- 

 ored with piuk, purple and bi'own fatty deposits and the markings are 

 more conspicuous than in the American Uurycercus, which is itself 

 often brightly spotted with blue or purple. The aspect in the water 

 is between that of Uurycercus and Daphnia. 



The first mention made of any member of this genus in America is 

 Say's description, repeated in Dekay's Crustacea of New Tork, of 

 Daphnia angulata. This description which follows is quite sufficient 

 to identify the genus, and indeed to indicate that either 8. americanus 

 or a related form is intended, but it is hardly competent to alter names 

 the significance of which is quite clear. 



"Sides striate with numerous parallel minute oblique lines; hind 

 edge of the body with a prominent angle in the middle. Antennae 

 with four filaments on the upper and five on the lower branch. Color 

 white or red. Length 0.1 mm. Stagnant water in the forests of the 

 Southern states." 



* Simocephalus vetulus Mueller. 



Plates XLIV, Fig. 7; LII, Figs. 6-9. 



Daphnia vetula — Balrd, Herrick. 



Daphnia sima — Mueller, Latreille, Bosc, Ramdohr,Gruithuisen, Desmarest, Lamarck, 

 M. Edwards, Koch, Gmelin, Manuel, Jurine, Lilljeborg, Leydig. 



This commonest and one of the largest species is apparently dis- 

 tributed over the northern hemisphere and abounds in all the more 

 shallow lakes. The head is rounded in front and is not angled between 

 the prominence of the eye and the beak. The body is very large and 

 not abruptly angled above, the spine of the shell being inconspicuous 

 and high, so that the free posterior edges of the shell lack little of 

 equaling the greatest height of the shell. The shell is covered with 

 minute dense striations which spring from the free edges. The pig- 

 ment fleck is elongated in old specimens and the upper angle follows 

 up beside the suture separating the antennary basin from the rest of 

 the shell of the head. The antennules are ornamented with minute 

 spines. At the lower angle of the shell are three curved spines which 

 differ from the preceding filaments. The number of eggs which are 

 produced at once is truly immense. Under favorable circumstances 

 this species reaches a large size, falling little if any short of 3.0 mm. 

 8. vetulus lives, by preference, among the leaves of aquatic vegetation. 

 With us this species seems to live in the smaller pools as well as in 

 lakes of some size. I am not able to see any difference in this respect 

 between the various species. 



