474 Wisconsin Academy of Sciences, Arts, and Letters. 



querquensis Herrick and D. albuquerquensis Schacht are not 

 identical. The figure of the male fifth foot given by Schacht 

 is very d liferent from that figured by Herrick, and I think it 

 probable that it belongs to D. saltillinus Brewer. The figure 

 of the female fifth foot is of neither D. saltillinus nor D. aXbu- 

 querquensis, as both species have a short endopodite. Schacht 

 states that his D. albuquerquensis was found in connection with. 

 D. mississippiensis, and his figure would correspond very well 

 to the fifth foot of the female of that species. It seems proba- 

 ble, then, that Schacht's description is a composite of D. sal- 

 tillinus and D. mississippiensis, and that he had no specimens 

 of D. alhuquerquensis. 



DIAPTOMUS ASYMMETKICUS Sp. nOV. 



Plate XXV, fig. 6. Plate XXVI, figs. 1, 3, 4. 



A small species. The first cephalothoracic segment is long- 

 er than the three following. The second, third and fourth 

 segments are about equal in length, the fifth somewhat longer. 

 The lateral expansions of the last thoracic segment are anned 

 on each side with an acute spine. 



The first segment of the female abdomen is much longer 

 than the rest of the abdomen. It is expanded laterally at a 

 little less than one-third its length ; the dilatations are armed 

 with acute spines which are slightly recurved. The dilatation 

 on the front of the segment is very pronounced. At about 

 two-thirds the length of the segment, and on the right side, is 

 a blunt, rounded projection, which is much more prominent 

 than the lateral dilatation. The second segment is short. The 

 third segment is fully four times as long as the second, and is 

 about equal in length to the furca. The distal end of the fur- 

 cal ramus is nearly twice as wide as the proximal ; the f urcae 

 are ciliate on the inner margin. 



The antennae are 25-segmented, and in the female extend 

 beyond the tip of the furcae. The right antenna of the male 

 is much swollen anterior to the geniculating joint. The an- 



