244 Illinois State Laboratory of Natural History. 



second basal segment of the right leg, the two spines on the 

 outer margin near the base of the hook of the second seg- 

 ment of the right outer ramus, the serrations of the apical 

 spine of the second segment of the left outer ramus, and the 

 process on the inner margin of the first segment of the same 

 ramus. De Guerne and Richard omit the tubercle on the 

 inner apical angle of the first basal segment of the left leg, 

 the hairs on the inner margin of the second segment of the 

 left outer ramus, and the hyaline lamina on the process of 

 the second segment of the right outer ramus, which is figured 

 by Nordqvist as being on the outer margin only, while it is 

 really on both. Nordqvist also fails to show the spines at the 

 base of the outer margin of this hook. 



I have had no opportunity to examine specimens of the 

 marine genus Centropages, but the drawings of the fifth pair 

 of legs of the female of L. macrurus and of C, hamatus are 

 so similar that it is hardly to be wondered at that de Guerne 

 regarded the two forms as belonging to the same genus. The 

 fifth pair of the legs of the males also show the same general 

 structure in the two genera, although they differ materially 

 in detail. 



L. macrurus is the only species of the family Centropagida 

 which is common to Europe and America. This is probably 

 due to the fact that it occurs in both fresh and salt water, 

 and thus the Atlantic offers no barrier to its distribution. It 

 has been recorded from Sweden, Norway, and Finland, from 

 the Kara and Baltic Seas and the Gulf of Finland, and from 

 the ocean off Spitzbergen ; and it is probably widely distributed 

 in the countries of northern Europe and Asia. In America it 

 was first recorded from Lake Michigan (Forbes, '82), and 

 later, under the name of L. macrurus auctus, from Lake 

 Superior (Forbes, '90). Marsh ('93 and '95) found it in 

 Green Lake, Wisconsin, in Lake St. Clair, Michigan, and in 

 Lake Huron. 



