Lehmann—Variations in Form and Size of Cyclops . 281 
It appears to be but a modified condition of the above species, 
from which it differs in its slender form and especially in the 
very slender caudal stylets. The outer caudal seta is reduced 
to a short ciliate thorn. The fourth foot is also modified by 
the great enlargement of the spines and the reduction of the 
setae. The number of the setae is the same, but they are differ¬ 
ently disposed.” Marsh describes this same species: “Plate 
IV. Tigs, 11 and 12, Turca slender, longer than the last two 
abdominal segments, lateral spine at two-thirds the distance 
from base to extremity. Of the terminal setae, the outer is a 
short blunt spine, the inner slender and somewhat longer. * * 
The armature of the terminal joints of the swimming feet is 
as follows :** 
Fourth foot 
Inner hr. 
ex. ‘1 sp. 
ap. 2 sp. 
in. 2 setae. 
**The fifth foot is two-jointed. The basal joint is very broad 
and is armed with one seta. The terminal joint is armed with 
one seta and a short spine.** It is widely distributed in lakes 
and ponds, and is a pelagic species, though sometimes occurring 
in littoral collections. / 
“I have had some doubt as to whether this should be consid¬ 
ered a distinct species. In most of its structural features it 
closely resembles americanus, and I have suspected it to be a 
pelagic variety of that species. I have specimens of ameri¬ 
canus with elongated furca like brevispinosus, and I have speci¬ 
mens of brevispinosus in which the outer terminal seta of the 
furca is slender and plumose as in americanus. Tor the differ¬ 
ence in the armature of the swimming feet, however, I have as 
yet found no intermediate forms, and so must, for the present, 
at least, consider the two as distinct,” Marsh’s description of 
americanus is as follows: “Plate IV, Tigs 8-10. Turca 
about three times as long as its average breadth, the lateral 
spine situated well toward the end. The first and fourth ter¬ 
minal setae are short, slender and plumose, nearly equal in 
length—** 
