Marsh — North AmeHcan Species of Dia'ptomus. 451 



dopodite of the female fifth foot. It resembles D. stagnalis 

 in the antennal armature and in the general form of the male 

 fifth feet ; but it differs in the male fifth feet, in the form of 

 the second segment of the exopodite, and in the form and size 

 of the endopodite. It differs in the female fifth feet in the 

 fact that the terminal spines are shorter, and that the third 

 segment is not distinct. 



DIAPTOMUS CLAVIPES Scliacht. 



Plat© XX, fig. 9. Plate XXI, figs. 1, 5, G. 



1897. Diaptomas davipes Schacht, p. 178; pi. XXXIV, figs. 



1-3 ; pi. XXXV, figs. 1, 2. 



1898. Diaptomus nehrasl-cnsis Brewer, p. 123 ; pi. VII, figs. 



1-4. 

 1902. Diaptomus davipes Beardsley, p. 45. 

 1905. Diaptomus davipes Pearse, p. 147 ; pi. XIII, fig. 6. 



A large species. The first segment of the cephalothorax is 

 equal in length to the three following. The last segment of 

 the cephalothorax is armed with two small lateral spines. 



The first seginent of the female abdomen is longer than the 

 rest of the abdomen. It is much dilated in front and some- 

 what laterally. The lateral dilatations are not abrupt as in 

 many species. There are two small lateral spines. The third 

 segment is very short. The fiirca is about equal in length to 

 the two preceding segments. The furcal rami are ciliate on 

 the inner margin. 



The antennae are 25-segmented, barely reaching the end of 

 the furca. Tlie right antenna of the male is much swollen an- 

 terior to the geniculating joint ; the antepenultimate segment 

 is armed with a lateral hyaline lamella. 



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

 are rather small and blunt. The lateral hairs of the second 

 basal segments are of moderate length. The length of the 

 first seginent of the exopodite is less than twice its width. The 

 second segment is stout, and the hook is almost straight. It 



