254 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
terminal claw sinuate or irregularly curved. The stout seta on the outer margin of 
the second segment of this ramus is borne at about a quarter the length of the seg- 
ment from the distal end, and is approximately half as long as the segment to which 
it is attached. The inner ramus is a little longer than the basal joint of the outer. 
It is not dilated or otherwise modified, but terminates bluntly, bearing at the tip a 
covering of long cilia. 
The right antenna of the male is without notable distinctive characters. The 
antepenultimate segment is as long as the two following taken together; the fourth 
from the tip bears two long sword-like spines at its margin, both attached to its basal 
fourth ; the expanded segments are well armed with conical spines, straight and curved, 
but without hooks. 
Small lakelet near Gardiner, Montana. 
Epischura nevadensis, var. columbiae, n. var. (Plate xli, Figs. 19-21.) 
It is with pleasure that I report here the occurrence of another form of this inter- 
esting genus of North American entomostraea, the fourth or fifth thus far discovered. 
The first species described, E. lacustris , has been found in the Great Lakes, in the smaller 
lakes of Wisconsin and Minnesota, and at Portland, Oregon; the second, E. Jiuviatilis 
Herrick, has been seen only by the original describer of the species, by whom it is 
said to occur in Mulberry Creek, Cushman County, Alabama.* Epischura norden- 
sTciceldii Lillj., is from Newfoundland, and E. nevadensis from lakes Echo and Tahoe, 
the former in California, the latter partly in that State and partly in Nevada. The 
]) resent form occurs in Swan and Flathead lakes, in northwestern Montana, where it 
was the most abundant copepod in the open water. 
The absence of all representatives of this genus from the lakes of Yellowstone 
Park, evidently adapted to them, hints strongly at a limit of altitude to their distribu- 
tion. The highest locality from which any species has been reported is Lake Tahoe, 
said to be 6,250 feet above the sea; while the lowest lake of suitable size in Yellow- 
stone Park from which our collections were made was 1,200 feet higher than this. 
This topographical difference does not measure the biological difference, however, as 
the lower location is also more than five degrees south of the Yellowstone lakes. 
Disregarding the doubtful ftuviatilis , the species of Epischura are, so far as known, 
of north temperate range in North America. The form least modified, both in abdomen 
and fifth legs, is the Newfoundland species, nordensTciceldii , and the most modified in 
both is nevadensis , lacustris standing intermediate. The new form, again, is interme- 
diate between lacustris and nevadensis proper and may be roughly characterized as 
uniting the characters of the fifth legs of the male and female and the caudal setae of 
nevadensis with those of the abdomen of the male of lacustris. 
* Herrick’s species hardly seems to belong to this genus. The abdominal processes are described 
as projecting from the left side of the abdomen, and consequently cannot be homologized with those 
of E. lacustris, all of which are developed from the right, and the fifth foot of the male is scarcely 
c apable of close comparison with the corresponding appendages of undoubted Epischura. The differ- 
ence reported in the position of the hinge in the antennas of the male also points to a deep-seated and 
fundamental distinction, not easy to reconcile, it must be admitted, with the agreement in ftuviatilis 
and lacustris with respect to the inner ramus of the swimming legs, the fifth legs of the female, and 
the caudal setae. 
