324 Merrill—Structure and Affinities of Bunops Scutifrons. 
MEASUREMENTS OF ANTENNAE. 
Basal Joint. 
Extreme length. 0.402 mm. 
Average width. 0.061 mm. 
Width at free end. 0.052 mm. 
Rings at base. 0.175 mm. 
Ventral Branch. 
Basal joint, length. 0.196 mm. 
Basal joint, width. 0.024 mm. 
Basal seta, length. 1.240 mm. 
Second joint, length. 0.054 mm. 
Second joint seta, length. 1.050 mm. 
Terminal joint, length. 0.070 mm. 
Dorsal Branch. 
Basal joint, length. 0.026 mm. 
Second joint, length. 0.070 mm. 
Second joint, length of spine... 0.001 mm. 
Second joint, width. 0.022 mm. 
Third joint, length. 0.070 mm. 
Terminal joint, length. 0.087 mm. 
Terminal joint, width. 0.017 mm. 
Terminal setae, length. 0.875 mm. 
POST-ABDOMEN. 
PI. XV, Fig. 6. 
The post-abdomen is large, triangular, broad above, but 
greatly flattened below. It is divided into two parts by a 
notch on the dorsal side just anterior to the anus. The anus,, 
therefore, opens on an elevation at a short distance from 
the terminal claws. As in Cladocera generally the anus 
is an elongated slit. Here it lies between two folds of in¬ 
tegument. The fold on each side is provided with three 
spines posteriorly, and is bordered by a fringe of setae 
