514 GEOLOGICAL SURVEY OF /THE TERRITORIES. 
greater length than width. The antenne of the second pair (claspers) 
are more or less broadened in the males, and have principally on their 
second interiorly directed part a flattened form. These antennz are 
either without appendages, or only with a few little developed append- 
ages, in the form of rounded or knob-like protuberances on the interior 
margin of their anterior, outwardly directed, or finally with small ap- 
pendages in the shape of denticular spines near their base. For the 
most represents the little developed, terminally and often laterally, 
bristled abdominal furca, a simple prolongation of the last segment of 
the abdomen; the furcal branches are conical or stylet-shaped, seldom 
tabulate. Parthenogenesis is known to occur in this genus. 
Genus BRANCHIPUS. 
Nine apodous abdominal segments (Branch. stagnalis excluded ?), of which 
the first two bear the external sexual organs, the last segment located before 
the furca being not larger, but mostly smaller than its preceding. The an- 
tenn of the second pair (claspers) in the males have their first joint 
stout, often with much developed appendages on their sides or at their 
base, in the shape of digitate processes or denticular tuberosities, the 
second part being more slender and narrower than the first; in the op- 
posite case the antenna is terminally divided into several branches. The 
generally much developed, laterally and terminally, bristled furca has 
its branches nearly always of a tabulate form, which are separated 
from the last segment by an articulation. Parthenogenesis is unknown 
in this genus. 
Eleven pair of legs are the common character for these two genera, 
distinguishing them from the genus Polyartemia Fischer, which has 
nineteen pair of legs and a lesser number of apodous segments of the 
abdomen. 
OpEssA, May 5, 1877. 
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