282 



WOLCOTT. 



[VOL. I. 



FIG. 3. A. indistinctiis $? outer 

 side right palpus, x about 125. 



the females of the other species. The body is regular in out- 

 line and measures about .8 mm. in length, with the same divi- 

 sion of the surface into areas as in A. abnorniipcs. The palpi 

 are relatively stouter (Fig. 3), while the epimera cover, as in 



that species, most of the ventral sur- 

 face. The legs are relatively long 

 and moderately stout, the fourth two 

 fifths longer than the body, while the 

 accessory tip on the claw is one third 

 the length from the distal end. Each 

 lateral sexual plate is in two parts, 

 with the acetabula three and six, re- 

 spectively ; in one instance four and 

 five on one side, three and six on the other. 



Specimens were taken at Lake St. Clair, Mich., and confused 

 with the following species until mounted and subjected to a 

 careful microscopical examination, when the differences became 

 apparent. 



IV. A. scrratus n. sp. 



The third and largest member of this group just referred to, 

 averaging in length about i.i mm., and with a regular outline. 

 Surface of the body marked as in preceding forms. The palpi 

 are relatively much stouter 

 (Fig. 4), while the legs are 

 a trifle more slender and not 

 so long proportionately. The 

 fourth leg is only one eighth 

 longer than the body in the 

 male, and in the female, 

 where all the legs are shorter, 

 it is even less than the body 

 length. In the male a larger 

 or smaller number of the 

 stouter spines on all the legs are serrate along both margins ; 

 on only the basal segment of the first, on each successive leg 

 more, till on the fourth are serrate spines on each segment, 

 and on the distal segment is a row of very prominent, flattened, 



FIG. 4. A. serratus $ outer side right 

 palpus, x about 125. 



