NORTH AMERICAN SPECIES OF THE GENUS ATAX 223 



MEASUREMENTS: 



Male Female 



Length of body 0.740 mm. 0.867 mm. 



Width of body (extreme) 0.637 mm. 



Length of leg 1 0.785 mm. 0.698 mm. 



Length of leg II 1.066 mm, 0.890 mm. 



Length of leg III 1.050 mm. 0.870 mm. 



Length of leg IV 1.076 mm. 1.020 mm. 



Palpus (from another speci- 

 men of same size in case 



of male) 0.347 mm. 0.380 mm. (approx.) 



Types in the author's collection; co-types have been deposited in the 

 collection of the Zoological Laboratory, University of Nebraska, in the 

 Museum of Comparative Zoology of Harvard University, in the United 

 States National Museum, and in the Kgl. Museum fur Naturkunde in 

 Berlin. 



Specimens of females of this species taken at Lake St. Clair, 

 Mich., were confused with the following species and their 

 identity not detected till mounted and subjected to a careful 

 microscopical examination, when the differences between the 

 two species became apparent. Hence no statement can be 

 made as to the definite source of the specimens. 



It was therefore with much pleasure that upon looking over 

 the collection of mites from Prof. H. M. Kelly, this species 

 was found in considerable numbers — 60 males and 115 females 

 altogether. They were taken from TJ. alatus and TJ. gracilis 

 from the Illinois River at Havana, Ills. ; from TJ. gracilis from 

 the Spoon River at Duncan's Mills and Bernadotte, Ills. ; and 

 from "TJnio spp." from the Cedar River at Mt. Yernon, 

 Iowa. Specimens were also found in the material from Mr. 

 M. Ricker. 



7. ATAX SERRATUS WOLCOTT. 



Atax serratus Wolcott, 98; 282. 



Atax serratus resembles very closely the two preceding species in the 

 appearance of the palpi and in the form of the claws and to a lesser degree 

 in the outline of the genital field and of the epimera. It is larger, pro- 

 portionately more elongated and the body of the male is only slightly 

 pyriform. The legs are proportionately shorter and IV of the male is not 

 modified. They are characterized by the presence of numerous serrate 

 spines which suggests the specific name proposed. 



The body is oval in form, bluntly and evenly rounded at both ends in 

 the female, that of the male with a slight posterior emargination. Its 



