The Fresh Water Copepoda of the Canadian Arctic Expedition 
1913-18 
By C. DWIGHT MARSH 
U. 8. Department of Agriculture 
The collections of the Canadian Arctic Expedition were of especial interest 
from the standpoint of geographical distribution, as the localities included a 
region from which no previous collections had been made. Copepoda have 
been collected in Iceland, Greenland, Newfoundland, Alaska, and lakes in the 
province of Saskatchewan, but the region north of Saskatchewan is practically 
unexplored, so far as entomostraca are concerned. If it is assumed, as is generally 
done, that with the retreat of the ice of the glacial period, there was a migration 
towards the north of the species adapted to the conditions of cold water, we should 
expect to find, so far as North America is concerned, the more primitive forms 
in the arctic or sub-arctic regions. These forms might continue further south 
as a fauna relicta, where altitude made a suitable environment, but where 
climatic conditions were radically changed, changes in structure would occur 
which might result in the formation of new species. That this has actually 
occurred in North America is very probable, as has been indicated in Marsh, 
1907, pp. 384 and following. Therefore collections from an unexplored region 
of the northern part of the continent are of particular interest, and itis to be 
hoped that further collections can be made both in the Arctic and in the region 
immediately south, of which practically nothing is known. 
All the specimens were collected by Mr. Frits Johansen, naturalist on the 
expedition, in various lagoons, ponds, and lakes along the Arctic coast; es- 
especially at the two winter headquarters of the expedition, Camden bay, Alaska, 
and Dolphin and Union strait, Canada. At the other places only shorter visits 
were made in the summer time. 
Genus Limnocalanus. 
Limnocalanus johanseni, n. sp. 
Plate I, Figs. 1-8. 
The first segment of the cephalothorax is nearly one-half the length of the 
cephalothorax. The front is armed with two projections. The last cephalo- 
thoracic segment is rounded on the sides and each side is armed with a small 
spine, which may be sharp, as in PI. I, fig. 1, or blunted, as in PI. I, fig. 2. 
The abdomen of the female, Pl. I, fig. 3, consists of three segments: the 
first segment is somewhat expanded laterally and is about twice as long as the 
second; the third segment is slightly longer than the second. The branches of 
the furca are three times as long as wide and are about half again as long as the 
third segment; they are ciliated on their internal margins, and have the typical 
armature of sete. 
The male abdomen, PI. I, fig. 4, consists of five segments, of which the first 
three are about equal in length; the fourth and fifth are somewhat shorter 
and about equal to each other. The length of the furcal branches is about 
three and one-half times the breadth, and about equals the two preceding 
segments. The furce are ciliated on the internal margins. 
The antennz of the female when reflexed reach the second abdominal seg- 
ment. The cephalothoracic appendages of the female are like those of L. 
