130 
and with the breadth of the peduncle equal 
to 0.4 of its length. In N. awatschensis the en- 
tire eyestalk is slightly less than 1.5 times as 
long as the cornea is broad, with the cornea 
occupying 0.5 the length of the entire stalk, 
and the peduncle is 0.5 as wide as the stalk 
is long. The specimens examined agree with 
N. mercedis and N. intermedia. 
Thoracic endopods: Tattersall reports that the 
sixth joint of the thoracic endopods is divided 
into 8-10 secondary joints in N. mercedis, into 
7-11 joints in N. intermedia, and into 6-8 
joints in N. awatschensis. Smaller specimens of 
N. mercedis from Washington have 6-8 joints, 
whereas the larger have 8-10; specimens from 
Alaska approaching N. intermedia have 7-10 
joints. 
Fourth pleopods of the males: In N. mercedis 
and N. awatschensis the terminal article of the 
outer branch of the fourth pleopods of the 
males is supposed to be 0.25 the length of 
the proximal joint and definitely shorter than 
the terminal setae, whereas in N. intermedia 
the terminal article is 0.5 the length of the 
proximal and longer than the setae. However, 
in mature specimens from Washington the 
terminal article is 0.3 to 0.2 the length of the 
proximal, whereas immature specimens have 
the proportions given for N. intermedia. 
Telson: Tattersall reports the telson to be 
similar in N. mercedis and N. intermedia, being 
twice as long as broad, the apex 0.2 the 
breadth of the base and the lateral spines 
shorter than the spaces between their bases; 
the only difference is that in N. mercedis there 
are 15 lateral spines (as shown by Tattersall 
in fig. 72), whereas in N. intermedia there are 
13-21 lateral spines. He reports that the telson 
of N. awatschensis is 1.75 times as long as 
broad, the apex is 0.25 the breadth of the 
base, and the posterior of the 17-21 lateral 
spines are longer than the spaces between 
their bases. In the specimens from fresh water 
from Washington the tip of the telson is about 
O. 12 the breadth of the base, but in some of 
the more brackish- water specimens from 
Washington and Alaska the tip is 6.25 to 0.2 
PACIFIC SCIENCE, Vol. VIII, April, 1954 
Fig. 1. 'tseomy sis awatschensis (Brandt), specimen from 
Naknek River, Alaska, a. Fourth pleopod of male; 
b, telson, showing extreme condition of the spines. 
(Both drawings to the same scale.) 
the breadth of the base. The number and 
length of the lateral spines are also variable, 
even those from the same locality; for ex- 
ample, some of those from Naknek River had 
spines longer than the spaces between their 
bases, therefore more like N. awatschensis, 
whereas in others the spines were shorter, like 
the other two species. The length-breadth re- 
lationship showed similar variation. 
With this summation it can be seen that the 
three species were separated by rather small 
differences, but such differences, were they 
to remain constant, would have been adequate 
for the separation of the species. However, 
the specimens examined showed all these 
characteristics to be variable beyond the lim- 
its set for the separation of the three species. ’ 
The sole exception may be found in the rather 
slight differences reported for the eyes, and 
