North American Centropagidce. 263 



Ideality as the type, — Normal, 111., — and from other speci- 

 mens collected at various times and places in Illinois, Indiana, 

 and Michigan. 



This species, the type of the genus, was first described in 

 the "American Naturalist" (Forbes, '82a), and de Guerne 

 and Richard, Forbes, Herrick, and Marsh have since published 

 descriptions and figures. Scopiphora vagans Pickering is, as 

 de Guerne and Richard, Herrick, and Marsh have said, 

 probably identical with Epischura lacustris, but this can never 

 be definitely determined since the following quotation is all 

 that has been published concerning S. vagans. 



"Genus Scopiphora, Pickering. Body small. Eye single, 

 in the anterior margin of the shield. Antenna; large, and as 

 long as in the preceding genus ^Cyclops], and has the same 

 motions in the water. Abdomen terminating in two styles 

 each with three setie; a brush under the last or last three 

 joints. Ovaries none. Legs spiny. 



" S. vegans (Pickering) MSS."* 



This is, of course, too meager a description upon which to 

 establish a genus, and the writers mentioned above, as well 

 as Dr. Schmeil ('98), have considered it insufficient and 

 allowed Forbes's name to stand. Herrick explains the "brush" 

 as some parasitic growth. May it not rather have been the 

 fifth, and perhaps the fourth, pair of legs projecting straight 

 backward under the abdomen which caused this appearance? 



In the following three paragraphs are noted the points in 

 which my observations differ from those of previous writers 

 as shown by their descriptions and figures. 



The abdomen of the male is very complicated in its seg- 

 mentation, and in the original description (Forties, '82a) was 

 described as having processes on the second, third, fourth, 

 and fifth segments. All figures published previous to the 

 appearance of " A Preliminary Report on the Aquatic In- 

 vertebrate Fauna of the Yellowstone National Park, etc." 

 (Forbes, '93), including those of de Guerne and Richard's 

 " Revision," were incorrect. In Forbes's paper attention was 

 called to the fact that the fourth segment was without a 



* See Pickering, '44. 



