156 Wisconsin Academy of Sciences, Arts, and Letters. 
Koenike’s paper did not include any account of the limbs; a 
description is therefore added here. 
The palpi show no striking peculiarities. The fifth segment 
is unforked and hears a bristle; the fourth is. the largest and 
has a blade-like bristle on the outer edge. The legs increase 
in size from the first to» the fourth. Each ends in two pointed 
claws. The first and second pairs bear a few bristles' and 
thorns with short fine hairs on the 1 last joint. The third pair 
of legs resemble the anterior pairs but have more bristles, be¬ 
side® a few long swimming hairs on the third, fourth and fifth 
segments. The fourth pair of legs have thorns or bristles on 
all segments; the third, fourth and fifth segments having in 
addition long swimming hairs. The fourth segment is nearly 
twice as long as the relatively short sixth;; the process so char¬ 
acteristic of male Arrenuri is hardly developed. The first 
leg is 0.56 mm. long; the fourth, 0.77 mm. 
This is one of the rarer Arrenuri, only five individuals hav¬ 
ing been found, and the females are unknown. These speci¬ 
mens were collected in Lake Wingra, Lake Mason shallows, 
and the borders of Green Lake. 
Arrenurus cylindratus Piersig. 
Eig. 8, a—d, PI. XVII. 
Arrenurus cylindraius Piersig, 1896 (a) ; S. 441. 
Arrenurus cylindratus Piersig, 1897; S. 288-289, Eig. 112. 
Arrenurus cylindratus Piersig, 1901; S. 84-85. 
This specie® has a large stout body with an appendage less 
than half as long. It resembles A. Krameri Koenike and A. 
securiformis Piersig in general form and in the structures on 
the appendage, but differs from both in the longer body and in 
the details of the shorter appendage. It is one of the largest 
as well as rarest of the Arrenuri. Only one individual was 
found; this was in Mirror Lake, September, 1893. The color 
was a dull brownish green. The entire length was 1.15 mm; 
width, 0.7 mm; length of the appendage, 0.53 mlmi. 
The body is slightly arched, and the dorsal shield is higher 
than the side walls. Several short hairs were found here. The 
