248 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The abdominal segments are as long as the cephalothoracic segments two to five 
taken together, and the furca is as long as the last three segments. The first segment 
of the abdomen is broadest in front, where its width is nearly as great as its length. 
The second is as broad as long, the third and fourth equal, the fifth a little shorter, 
the last with a row of fine spinules around the base of the rami. 
The width of each ramus is contained nearly eight times in its length. Besides 
the lateral spilie — situated a little before the posterior third of the ramus — there is a 
cluster of two or three minute spines at its anterior fourth. The outer and inner 
terminal set® are reduced to short subequal spines about twice as long as the ramus 
is wide. The other set* are slender, plumose, the inner nearly twice as long as the 
outer of each pair. 
The antennae are rather stout and short, seventeen-jointed, reaching to the end 
of the second segment. They are without special structures or appendages. 
The last segments of the thoracic legs ate armed as follows: 
First pair: outer ramus, one spine and two set* at tip, two set* within, and one 
spine without; inner ramus, one spine and one seta at tip, three set* within, and one 
seta without. 
Second pair: outer ramus, one spine and one seta at tip, three set* within, and 
two spines without; inner ramus, one spine and one seta at tip, three set* within, and 
one seta without. 
Third pair: outer ramus, two spines and one seta at tip (one spine twice as long 
as the other), three set* within, and one spine without; inner ramus, one spine and 
one seta at tip, three set® within, and one seta without. 
Fourth pair: outer ramus, two spines and one seta at tip (one spine double the 
length of the other), three set* within, and one spine without ; inner ramus, two spines 
at tip (one double the length of the other), two set® within, and one seta without. 
The fifth pair is two-jointed, the basal joint broad, Quadrate, with a seta at its 
outer angle; the second cylindrical, with one long and one short seta at tip. 
Length, without set®, 1.34 millimeters. 
Described from females only. 
Cyclops capilliferus, n. sp. (Plate xl, Figs. 14-17, and Plate xli, Fig. 18.) 
This is a symmetrical, compact Cyclops , with the cephalothorax closely articulated, 
widest at the middle, and the sides regularly convex, with the abdomen narrow and 
slender, with three well-developed caudal set®, and sixteen-jointed antenn® bearing 
several very long set®. 
The abdomen, with caudal furca, is contained a little less than twice in the ceph- 
alothorax, and the breadth of the latter is just half its length. *First segment very 
long, five times the length of the second; second and third equal; the fourth very 
short, on the median line semicircularly excavate behind. The abdominal segments 
in the female diminish regularly in length from first to last. The caudal rami are 
twice the length of the last segment and one-fourth as broad as long. The lateral seta 
is placed a trifle beyond the middle of the ramus; the outer terminal seta is a short 
naked spine; the other three are well developed and plumose. The inner and outer 
of these three are of nearly equal length, the latter a little the longer, the middle one 
much the longest one of the group. 
