Simocephalus exspinosus. 293 



Gruber and Weismaun say of 31. paradoxa "dass hier von einer 

 polygonalen Felderung durchaus keine Kede 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 31. banffyi, Daday 

 ('88, p. 112, PI. Ill, fig-. 1.); but in that species the hairs are 

 found all over the h^ad and extend upon the carapace, while in 

 all specimens of 31. Jtagellata, 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 31. affinis 

 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 31. affinis. 



SlMOCEPHALUS 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 iu 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. 



