Marsh—North American Species of Diaptomus. 469 
ridge extends across the posterior surface of tlie segment. The 
terminal hook is falciform and nearly equals in length the 
whole right foot. The endopodite is small and slender, consid¬ 
erably exceeding in length the first segment of the exopodite. 
The left fifth foot in length reaches the distal extremity of 
the first segment of the exopodite of the right foot. The first 
segment of the exopodite is somewhat longer than broad and is 
armed on its inner margin with small hairs. The second seg¬ 
ment is almost circular in outline, and also has the inner mar¬ 
gin setose. It is tipped with a finger-like process and with a 
longer slender spine. The endopodite is slender, somewhat 
conical in shape, and reaches to about the middle of the second 
segment of the exopodite. 
Length of female, 1.13 mm. Length of male, 1.069 mm. 
This species was found in collections made by Professor Birge 
at Guzman and Milneburg, Louisiana. In the Guzman collec¬ 
tions it was associated with D. mississippiensis. The form of 
the male fifth feet, however, and the dorsal process of the female 
make it easy to distinguish the two species. The particularly 
distinguishing features of D. dorsalis are the hyaline append¬ 
ages of the segments of the right male fifth foot, and this 
dorsal process. The process very probably resembles that in 
D. gibber Poppe, but as DeGuerne and Richard give no figure, 
one cannot be certain. 
diaptomus saltillixus Brewer. 
Plate XXIII, figs., 4, 6, 7, 10. Plate XXIV, fig. 1. 
1897. Diaptomus albuquerquensis Schacht, p. 146 ; pi. XXVII, 
figs. 2, 4. 
1898. Diaptomus saltillinus Brewer, p. 127; pi. VII, figs. 5-9. 
1905. Diaptomus saltillinus Pearse, p. 148; pi. XIV, figs, u, 
10 . 
Of moderate size. The first cephalothoracic segment equals 
in length the three following. The last cephalothoracic segment 
is expanded in lateral lobes, each of which bears two minute 
