Marshall—Ten Species of Arrenuri. 
159 
the last half of the appendage (fig. 10, a and c, h). The end 
of the appendage is bowed out a little in the middle, scarcely 
scalloped. The sides of the appendage are nearly parallel. 
There are several stout hairs whose positions are indicated 
by the accompanying figures. The epimera show no peculiari¬ 
ties. The genital area is narrow, though not always as narrow 
as shown in Fig. 10, b, and resembles that of A. truncatellus; 
the outline is indistinct. 
The distinguishing feature of the palpi is the great length 
of the fourth joint. The fifth is double^pointed. Bristles are 
not numerous. The legs named in order of length are the 
first, the third, the second, the fourth, with the greatest in¬ 
terval between the last two. The first and second are much 
alike, the segments increasing in length from the first to the 
sixth. All, especially the second and third, bear 1 bristles and 
short curved hairs', excepting the sixth, which has many short 
fine hairs. The third pair of legs have more bristles and long 
hairs on the fifth segment. The last pair of legs are stout with 
the exception of the last segment; the fourth is longest and has 
the usual process with a tuft of hairs. The third segment has 
unusually long, hairs and a short point on its distal extremity. 
The color is light greenish blue, with indistinct markings 
a:s in A. globaior. The length is 0.8 mmi; the width, 0.5 mm. 
Arrenurus Birgei is rather common. Several individuals 
were found in the following places: Lake Wingra,, Mirror 
Lake, borders of Green; Lake and Lake Spooner, pond at Tar¬ 
paulin Cove near Wood’s Hole. 
This species has been named for Dr. E. A. Birge of the Uni¬ 
versity of Wisconsin, at whose suggestion this work on the Ar¬ 
renuri was begun, and without whose continued assistance it 
could not have been carried on. 
