Nos. 455-456-] ^VEl^ SPECIES OF DIAPTOMUS. 



inner surface is ciliated. The inner ramus is short and hairy 

 at the tip. 



The female fifth foot (Fig. 3) bears a large tapering spine at 

 the outer distal angle of the first basal segment. The second 

 basal segment is triangular and provided with the usual lateral 

 hair. The outer ramus is three segmented. The first and 

 second segments are about equal in length. The second 

 segment is tapering and along the center of its inner side is 

 armed with strong teeth and is usually with two or three small 

 teeth on the outside. The second segment has a short spine 

 above the third segment. The third segment is small and is 

 armed with a long and a short spine. The inner ramus is not 

 half as long as the first segment of the outer ramus and is two 

 segmented. The second segment is armed with two terminal 

 spines with delicate hairs between them and a lateral spine on 

 the inner side. 



Length: Female 1.69--1.83 mm. Male 1.61-1.67 mm. 



The specimens from which this species is described were col- 

 lected by Mrs. Frank Lehmer, July 22 to August 7, 1904, in 

 Mexico City, Mexico. It was apparently abundant at that time, 

 as it occurs in most of the dredgings made. 



This species was associated with Cyclops viridis insectus 

 Forbes, Cyclops albidus Jurine, Canthocamptus sp..?, and an 

 ostracod. 



