428 Wisconsin Academy of Sciences, Arts, and Letters, 



segment is more than twice fiS long as broad, its outer margin 

 straight, and its inner with two setose convexities. It is termi- 

 nated Avith a finger-like process and a smaller spine nearer the 

 inner margin. The foot reaches to the end of the first segment 

 of the right exopodite. The endopodite is slender, attenuate 

 towards the apex, and reaches to about the middle of the second 

 segment of the exopodite. 



Length of the female, 1 to 1.1 mm. Length of the male, 

 hardly 1 mm. 



Lilljeborg states that the female carries only two eggs. This 

 was not true of the Wisconsin individuals, for they commonly 

 had as many as six. This was first described from material col- 

 lected in Greenland, where it is found as far north as Disco 

 island. It appears to be very abundant in the southern part of 

 Greenland. It was afterwards reported by DeGuerne and 

 Eichard from Iceland. (DeG. and R., '92.) It is found in 

 IsTewfoundland. It is perhaps the most common of the Diap- 

 tomi in the Great Lakes and Lake St. Clair. It occurs in a 

 number of lakes in the northern part of the southern peninsula 

 of Michigan, but these are, for the most part, connected rather 

 closely with the Great Lakes. In Wisconsin it is found in the 

 following lakes : Birch, ]\Iaple, Tomahawk, Stone, Chain o' 

 Lakes, Elkhart, Green and Geneva; all these are of the deeper 

 lakes of the state, although there are others, equal in depth to 

 some of these, where it is not found. The most southern point 

 at which the species has been found is Lake Geneva. To my 

 surprise, I did not find it in my collections from the ISTorthwest 

 Territory, but all those collections were in very shallow water. 

 One would expect to find it all over British America, wherever 

 the environment was favorable. I think it probable that it is 

 distributed all over North America east of the Rocky mountains 

 and north of the latitude of perhaps 43 degrees. 



