Marsh — North American Species of Diaptomus. 449 



my collections have been made, although, it is reported as oc- 

 curring not only in Illinois and Minnesota, but in Ohio, Ken- 

 tucky and Alabama. 



The segmentation of the fifth feet of the female would indi- 

 cate that this is one of the least specialized of the members of 

 the leptopus group. 



DIAPTOMUS COIs^IPEDATUS Sp. UOV. 



Plate XX, fig. 4. Plate XXI, figs. 2-4. 



A rather large species. The first cephalothoracic segment is 

 nearly as long as the succeeding three segments. The last 

 cephalothoracic segment has two minute spines on each lateral 

 lobe. 



The first abdominal segment of the female is somewhat less 

 in length than the rest of the abdomen and the furca. It is 

 dilated in front, and slightly dilated at the sides. The lateral 

 dilatations are armed with small spines. The second and third 

 segments are about equal in length, and are broader than long. 

 The rami of the furca are somewhat longer than the third seg- 

 ment and are ciliate on the inner margin. 



The antennae hardly reach the end of the furca. The right 

 male antenna is much swollen anterior to the geniculating joint. 

 The antepenultimate segment is armed with a hook-shaped proc- 

 ess, which is not strongly recurved; it is rather less than half 

 as long as the penultimate segment. 



The first basal segment of the female fifth foot has the usual 

 spine upon its posterior surface. The second basal segment has 

 the customary lateral hair. The first segment of the exopodite 

 is short and stout. The second segment is stout and prolonged 

 into the usual hook which is denticulate on the inner margin. 

 The third segment is represented by two spines. There is also 

 a third spine situated outside these two. The endopodite is 

 much longer than the first segment of the exopodite, is armed 

 with short hairs on the inner margin of the tip, and has two 

 rather long terminal spines. 

 29— S. & A. 



