Marsh — North American Species of Cyclops. 1105 



widely separated. Schmeil says that the length nearly equals 

 the last three segments. In our forms this is rarely the case, 

 the length being more generally equal to the last two and a 

 half of the third, or about three times the length of the last 

 segment. In some cases the rami are shorter yet, as in some 

 specimens collected in the Saskatchewan. The lateral seta is 

 situated at about two-thirds the length of the furca on the 

 dorsal surface. A row of spines extends from the outer 

 margin of the furca, on the dorsal surface opposite the seta, 

 curving nearly to the center of the furca, and then nearly to 

 the proximal end of the furca. Of the apical setae, the outer 

 is spine like and short, the inner is slender and somewhat 

 longer than the outer ; the longest of the two middle ones nearly 

 equals in length the cephalothorax. 



The first antennae (PI. LXXXI, fig. 2) of the female are 

 composed of eight- segments, are about two-thirds as long as the 

 first cephalothoracic segment, and in repose lie nearly at right 

 angles with the long axis of the animal. The fourth segment 

 is the longest, and the fifth bears a sensory seta. The setae 

 with which the antennal segments are armed, are, for the most 

 part, long and stout. The segments near the base are quite 

 stout, the first two being four times as wide as the terminal 

 segment. 



The external margins of the segments of the swimming feet 

 (PI. LXXXI, fig. 5) are armed with short, stout spines. The 

 spinous armature of the terminal segments of the exopodites of 

 the swimming feet is represented by the formula, 3, 4, 4, 3. 



The fifth foot (PI. LXXXI, fig. 4) consists of a single seg- 

 ment, and is armed with one spine and two setae. 



The egg-sacs, pi. LXXXI, fig. 3, lie alongside the abdomen, 

 and contain only a small number of eggs. 



The length of mature females varies from .7 mm. to .84 mm. 

 This is somewhat smaller than the figures given by Schmeil 

 for the European forms. 



Cyclops' fimbri'uius is not a common species, but is cosmopol- 

 itan in its distribution. 



The synonomy is given before the description, and no ex- 



