420 Wisconsin Academy of Sciences, Arts, and Letters. 
to the first, is almost triangular, and thinner on the inner mar¬ 
gin. The outer part of this segment is thicker, has a short 
spine in the middle, and ends in a short and obtuse process. 
The oblique apical margin of the inner surface has three small 
incisions. The inner margin of this segment is finely ciliate. 
The endopodite is one or two-segmented, slender, attenuate to¬ 
wards the apex, and reaches to about the middle of the second 
segment of the exopodite. 
Length of female, 2.3 mm. Length of male, 2 mm. 
Pound in the neighborhood of San Francisco. 
The above is the description of DeGuerne and Richard with 
some slight additions. The species has thus far been found 
only in the original locality. 
DIAPTOMUS BAKERI Sp. llOV. 
Plate XVI, figs. 4, 5, 6, 9. 
A small species. The first cephalothoracic segment is as 
long as the three following, the second, third and fourth being 
about equal in length. The last cephalothoracic segment is 
armed with two minute spines on each lateral lobe. 
The first segment of the female abdomen equals in length 
the rest of the abdomen, including the furcal rami. It is broad, 
dilated in front and laterally, with two small lateral spines 
about midway of its length. The second segment is very short. 
The width of the third segment is greater than its length. The 
furcal rami are about equal in length to the third segment, 
and are ciliate on the inner margin. 
The antennae are 2 5-segmented and barely reach the end of 
the furcal rami. The right antenna of the male is much swol¬ 
len anterior to the geniculating joint. The antepenultimate 
segment bears a hook-shaped process which is fully half as 
long as the penultimate segment. 
The first basal segments of the female fifth feet are armed 
with rather small spines. The lateral hairs of the second basal 
segments are short. The exopodite consists of three segments. 
The second segment is prolonged into a hook which is quite 
