ge tat Re AS eae 
ENTOMOSTRACA OF MINNESOTA. 169 
liar track. The length is sometimes 1.0 mm. The head is obscurely 
angulated in front of the antennules, which are large. The antennules 
of the male are long and have hooked seta at the end. 
The description of Ceriodaphnia cristata given by Birge would apply 
in almost every particular to C. megops, though he seemed to overlook 
the close conformity. The size is much less (0.7 mm.), and the post- 
abdomen seems more abruptly truncate; moreover the number of anal 
spines is less. The crest upon the dorsal margin may be the effect of 
prominences such as are described by P. E. Mueller; at any rate, in 
view of the fact that but few specimens were discovered, the sugges- 
tion lies near that C. cristata is the young or, at least, a reduced form 
of C. megops. Professor Birge writes that he now unites cristata with 
C. megops. 
Found at Southampton, Mass. 
Ceriodaphnia pulchella Sars. 
PLATE XLI, Frias. 14, 19. 
Very much like C. reticulata, but smaller. Head large, turgid, and 
angled in front of the antennules, forming almost aright angle; for- 
nices moderate; antennules rather large; shell oval, reticulated with 
double contour lines; post-abdomen of medium size, narrowed toward 
the end, slightly truncate. with about nine spines; terminal claws 
short, smooth. The flagellum of the male antenne is but slightly 
hooked, 0.5 to 0.6 mm. long. This species is not certainly identified 
from America, though a form with smooth claws and small fornices 
occurs with C. dentat« in some places. 
Ceriodaphnia rotunda Straus. 
PLATES: XLI, FIGs. 12; 23; XLII, Fre. 1. 
Daphnia rotunda—Straus, Baird. 
As said by Kurz, this species is not easily mistaken; the small head 
(only paralleled by the following), the very evident reticulations and 
the broad abdomen give it a peculiar habitus which is unmistakable. 
Head depressed, small, spiny below, not angulated; fornices promi- 
nent, thorned; body rotund, almost spined above; shell doubly retic- 
ulate; post-abdomen broad, with seven or eight anal spines; claws 
large, smooth. The male antennules are little larger than those of the 
female. I have not yet seen this species in America. 
