Copepoda Found in the Vicinity of Lincoln, Nebraska. 121 



in the streams, or in clear water where the vegetation is 

 slight. The coloring indicates nothing so far as identifica- 

 tion of species is concerned. Even Diaptomus sa?iguineus, 

 which is usually such a brilliant red, I found twice without 

 the slightest coloring. On the same day in adjacent pools 

 were found specimens of Cyclops america?ius beautifully 

 colored, those from one pool red with blue ovisacs, and those 

 from the other blue with red ovisacs. From a third pool the 

 specimens were all a handsome green from a protozoan 

 which covered them. 



The three genera of the locality belong to different families 

 and are immediately distinguishable. The Diaptomi have 

 long antennae with more than twenty joints. The body 

 nearly cylindrical, with a sharp constriction at the beginning 

 of the abdomen. The caudal furca bearing five nearly equal 

 setae and a sixth inner smaller one. The Cyclopes have shorter, 

 stronger antennae, with from ten to seventeen joints, a taper- 

 ing body, and a distinct constriction at the beginning of the 

 abdomen. The caudal fureae are long, and bear two long 

 setae (or three) with four others less developed. The Cantho- 

 campti have eight-jointed antennae, slightly tapering body, 

 with no constriction between the thorax and abdomen. The 

 caudal furcae bear one seta much longer than any other. 



KEY TO THE SPECIES OF DIAPTOMUS FOUND. 



A. The antepenultimate segment of the male right a?itenna 



unarmed. 



1. The inner ramus of the male right fifth foot equal to 

 the first joint of the outer. pallidus. 



2. The inner ramus of the male right fifth foot much 

 shorter than the first joint of the outer ramus. 



?iebraskensis n. sp. 



B. The antepe?iultimate joirit of the male right a?ite?ina bear- 



ing a short hook. 

 1. The inner ramus of the male left fifth foot longer than 

 the first joint of the outer ramus. 



a. The b'asal joint of the right foot produced and 

 sometimes jointed at the outer distal angle. 



sanguineus. 



3 



