1096 Wisconsin Academy of Sciences, Arts, and Letters. 
the last abdominal segment, and at the other extreme the slender 
form in which the furca may be three times as long as the last 
abdominal segment. The form shown in the plate, (PL 
LXXVIII, fig. 7) may be considered typical while the figure in 
plate LXXVIII, fig. 6 is of the slender form. The outer mar¬ 
gin of the furca is bordered by a row of short spines. These are 
not present in the male, and while always present in the female,, 
are very variable in size. It was noted by DeGuerne and 
Kichard ( ? 92) that the specimens collected at Bufisque showed 
these spines much less clearly than did the European speci¬ 
mens. Brady (Brady T906) also states that the serrulations 
in the Xew Zealand specimens are less marked than in those 
in Europe. There is much variability even in the same gen¬ 
eral region. These short spines are commonly much more 
prominent at the distal end of the furca. The lateral seta is 
at the end of the furca. Of the terminal setae the outer is 
short, sometimes spine-like, and, in the specimens with a short 
furca, commonly stands at nearly right angles with the furca. 
The second and third setae are prolonged; the third is rather 
less than twice as long as the second and only slightly exceeds 
the combined length of the abdomen and furca. The fourth 
seta is slender and weak, seldom much exceeding the first in 
length, and sometimes is shorter. 
The first antennae are twelve-segmented and reach to the 
third segment, or sometimes nearly to the fourth; their length 
is quite variable. The last three segments (PI. LXXVIII, fig. 
5) hear an inconspicuous hyaline membrane. Some of the 
European authors say that these hyaline membranes are some¬ 
times finely dentate, though commonly with entire margins. 
This dentation has never been noticed in American specimens. 
The spinous armature of the terminal segment of the exopo- 
dites of the swimming feet is 3, 4, 4, 3. 
The fifth foot (PL LXXVIII, fig. 8) is composed of a single 
segment. It is armed on its inner distal angle with a stout 
spine with serrate edges, and on its outer distal angle with a 
slender seta. Midway between these, on a prominent base is 
a long slender seta, considerable exceeding in length the outer 
seta. 
