Marsh—North American Species of Diaptomus. 467 
“The exopodite of the fifth pair of feet of the female is two- 
segmented, with the unguiform process of the second segment 
slightly curved, robust, denticulate on the middle part of the 
inner margin, the last teeth being broader and spine-like. The 
third segment is wanting and is represented only by two spines, 
the outer half as long as the inner. Endopodite one-segment- 
ed, hardly equal to the first segment of the exopodite, with the 
apex obliquely acuminate, provided with two quite long sub¬ 
equal spines. 
“The second segment of exopodite of right foot in male is 
very long, surpassing in length the first segment and the basal 
segment taken together. The marginal spine of this segment 
is placed within the middle. The terminal hook is slightly 
curved, with the inner margin denticulate. The endopodite is 
curved, ovate, broad, turning inward, mucronate at the apex, 
hardly reaching the end of the first segment of exopodite. In 
the left foot, the first and second segments of the exopodite are 
setose within, the second obovate, hairy towards the apex, and 
bearing two short spines, one of which turns inward. The en¬ 
dopodite is one-segmented, slender, equaling in length the first 
segment of the exopodite. 
“Length of female, about 1.5 mm.; length of male, 1.4 mm.” 
The above is the description as given by EeGuerne and 
Richard. It is added that the species was found in great 
numbers at “Multrooma Falls,” Oregon. As Schacht suggests, 
it is probable that the locality is Multnomah Falls. 
DIAPTOMUS DORSALIS Sp. nOV. 
Plate XXIII, figs. 8, 9. Plate XXIV, figs. 2, 3, 5, 6. 
A small species. The first segment of the cephalothorax 
considerably exceeds in length the three following. The last 
two cephalothoracic segments are confluent. The fifth segment 
has two dorsal teeth, the first of which is the more prominent 
and projects backward; the second is rounded and undulate on 
its anterior margin. The last segment bears two minute later¬ 
al spines. 
