Simocephalus exspinosus. 
293 
Gruber and Weismann say of M. paradoxa “.dass hier von einer 
polygonalen Felderung durchaus keine Rede sein kann”. 2. The 
basal teeth of the caudal claw are sometimes, though not always, 
larger than the others and thus give rise to a pecten. 3. 
The head of the young female is covered with short scattered 
hairs. In this regard the species resembles M. banffyi , Daday 
(’88, p. 112, PL III, fig. 1.); but in that species the hairs are 
found ail over the Imad and extend upon the carapace, while in 
all specimens of M. flagellata , they are confined to the dor¬ 
sum of the head. 4. The antennule bears posteriorly numerous 
long fine hairs. These are not mentioned by any European 
writer, but are not improbably present, as they are very easily 
overlooked. 
The head of the male projects greatly anteriorly and has no 
supra-ocular depression. The antennules are angulated at about 
the middle of their length or a little distad of that point. They 
bear 5-6 hooks on the outer end. The first foot bears a hook 
and a long.flagellum. 
Moina flagellata is readily distinguishable from M. afllnis 
at any age and in either sex. The differences between the 
two species in the female sex are sufficiently striking to enable 
me to determine the new form at the first glance, although 
I had never seen it before and did not expect to find it in the 
pool where it appeared, in which I had been accustomed to 
collect M. affinis. 
m 
Simocephalus exspinosus, Koch. 
Typical specimens of this species, not before recognized in 
America, have been found in collections from Green, Twin and 
Pioneer lakes and from Ashland. I find in Madison specimens 
resembling S. vetulus in all respects except the macula nigra, 
which is rhomboidal. I am doubtful whether to consider them 
as belonging to S. exspinosus or not. The differences between 
the two species in outline and serration of caudal claw do not 
seem to be constant. At least, I find that the form of the 
head of both S. vetulus and S. serrulatus is very variable. I 
also see no constant difference in the caudal claws of S. vetu¬ 
lus and S. exspinosus. 
