412 Wisconsin Academy of Sciences, Arts, and Letters. 



DIAPTOMUS KEIOIIABDI Mai'sll. 



Plato XV, figs. 2, 6, 9. 



1895. Diaptomus Reigliardi Marsh, p. 9; pi. I, figs. 1-4. 

 1897. Diaptomus Reighardi SchsLcht, p. 169; pi. XXVIII, 

 fig. 1. 



Of moderate size. The first eephalothoracic segment nearly 

 equals in length the rest of the cephalothorax ; the suture of 

 this segment is very distinct. The last eephalothoracic segment 

 is armed on each side with a minute spine. 



The first segment of the female abdomen is elongated, nearly 

 equaling in length the remainder of the abdomen and the furca. 

 It is dilated laterally and in front. Tlie lateral dilatations are 

 slight, and are armed on each side with a minute spine. The 

 second segment is about one-third shorter than the third. The 

 third segment is slightly shorter thaii the furcal rami. The 

 furcal rami are ciliate on the inner margin. 



The antennae are 25-segmented and reach to the end of the 

 furca. The right male antenna is swollen anterior to the genic- 

 ulating joint; the antepenultimate segment has no appendage. 



The spines of the posterior surface of the first basal seg- 

 n^ents of the female fifth feet are very small. The first seg- 

 ment of the exopodite is twice as long as wide. The second 

 segment is prolonged into a sharp hook which is denticulate on 

 the inner margin. The third segment is represented by two 

 spines. The endopodite is one-segmented, slightly longer than 

 the first segment of the exopodite, is setose at tip, and armed 

 with two rather long spines. 



The spines of the first basal segments of the male fifth feet 

 are moderately prominent. The second basal segment of the 

 right foot is about one-half longer tban broad. The lateral 

 hair is situated at about two-thirds of its length. The length 

 of the first segment of the exopodite is about equal to its width. 

 It bears a slight fold on its posterior surface near the distal 

 end. The second segment is more than twice as long as wide, 



