Marsh—North American Species of Diaptomus. 473 
about midway of its length, is an oblique ridge. The terminal 
hook is longer than the rest of the foot, regularly curved and 
finely denticulate on the inner margin. The right endopodite 
is one-segmented, about equal in length to the first segment of 
the exopodite, and is setose at the tip. 
The left foot reaches beyond the end of the first segment of 
the exopodite. The second basal segment is elongate, but 
shorter than the corresponding segment of the right foot. The 
lateral hair is situated at rather more than two-thirds the 
length of the segment. The first segment of the exopodite is 
about twice as long as wide; the inner margin is convex and 
setose. The second segment of the exopodite is about equal in 
length and width; it is terminated by a blunt process and a 
slender, curved spine; its inner margin has two setose pads. 
The endopodite is slender, one-segmented, equal in length to 
the first segment of the exopodite, and setose at the tip. 
Length of female, 1.765 mm. Length of male, 1.581 mm. 
Localities: Albuquerque, New Mexico, City of Mexico, and 
Hugo, Colorado. 
It was found impossible to get authoritative examples of this 
species, as the material was not preserved by Herrick, and the 
author was unsuccessful in dredging in the same locality. The 
description is from the material obtained in pools near Hugo, 
Colorado. Herrick does not mention or figure the tooth on the 
inner margin of the first basal segment of the right fifth foot of 
the male, or the dorsal tooth on the cephalothorax of the female. 
While it is possible that these features, which were not de¬ 
scribed either by Pearse, are local variations, it does not seem 
probable, inasmuch as the correspondence is so complete as far 
as the published descriptions go. It seems probable that these 
features were overlooked. 
It may be noticed that D. albuquerquensis, D. dorsalis and 
D. saltillinus are very closely related to each other, and it is 
possible that intermediate forms may be found. 
Schacht describes D. albuquerquensis from material collected 
in Florida. Just what Schacht had it is pretty difficult to tell, 
as he gives only two figures, but it seems evident that D. albu- 
