Ecology of Pelagic Amphipoda, I — Brusca 
deeper at night. His study was conducted in 
Antarctic waters. The present study, however, 
gives evidence that this species undergoes a typ- 
ical migratory activity toward the surface at 
night and retreats to deeper water during the 
day (Table 7). The daytime depth range was 
from 200 to 980 m and the nighttime range 
was from 80 to 650 m. The deep, positive, 
night samples probably indicate a descent of 
part of the population during the dark hours. 
Family cystisomidae 
Cystisoma fabricii Stebbing 
Thaumatops fabricii Stephensen, 1918:63- 
64, figs. 22-23; Pirlot, 1929:89. 
Cystisoma fabricii Stebbing, 1888:1333; Bar- 
nard, K. H., 1932:272-273; Hurley, 1956:10. 
A total of 31 individuals was collected from 
19 samples ranging in depth from 275 to 1100 
m. There is some evidence that this species 
TABLE 7 
Day and Night Depth Distributions for 
Primno macro pa 
DEPTH IN 
METERS 
TOTAL NO. 
SAMPLES 
NO. 
POSITIVE 
SAMPLES 
PER CENT 
POSITIVE 
Night 
0-50 
4 
0 
0 
50-100 
2 
2 
100 
100-200 
7 
4 
57 
200-300 
4 
1 
25 
300-400 
6 
3 
50 
400-500 
2 
2 
100 
500-600 
7 
3 
43 
600-700 
2 
2 
100 
700-800 
1 
1 
100 
800-900 
1 
0 
0 
900-1100 
3 
0 
0 
Day 
0-50 
2 
0 
0 
50-100 
2 
0 
0 
100-200 
2 
0 
0 
200-300 
4 
3 
75 
300-400 
4 
2 
50 
400-500 
5 
3 
60 
500-600 
5 
3 
60 
600-700 
4 
1 
25 
700-800 
3 
2 
66 
800-900 
4 
2 
50 
900-1100 
8 
4 
50 
387 
rises toward the surface at night but this is 
speculative due to the small number of indi- 
viduals collected. 
Cystisoma pellucidum (Suhn) 
Thaumatops pellucida Stephensen, 1918:64- 
66, figs. 19, 24-27. 
Cystisoma pellucidum Barnard, K. H., 1932: 
272; Thorsteinson, 1941:92-93; Hurley, 1956: 
10 . 
Four individuals of this species were taken 
in 4 samples ranging in depth from 275 to 
468 m. Although vertical movements are sus- 
pected for Cystisoma pellucidum, the data are 
too scant to support the suggestion. 
Family oxycephalidae 
Calamorhynchus pellucidus Streets 
Calamorhynchus rigidus Stebbing, 1888: 
1600, pi. 206; Bovallius, 1890:74; Stephensen, 
1925:189-191. 
Calamorhynchus pellucidus Streets, 1878: 
285, pi. 2, fig. 5; Bovallius, 1890:73-74, pi. 2, 
figs. 14-15; Fage, 1960:31-37, figs. 19-20. 
This is the first record of this species from 
Pacific North America. Only 1 specimen was 
collected during this study, at a depth of 360 
m. Although vertical migration is suspected 
from analysis of earlier works, no conclusions 
can be drawn here. 
Oxycephalus clausi Bovallius 
Oxycephalus clausi Bovallius, 1890:60, figs. 
4, 7, 8, 22, 54, 65, pi. i, figs. 19-24, pi. ii, 
fig. 1; Stephensen, 1925:188, chart 27; Bar- 
nard, K. H., 1930:433; Barnard, K. H., 1932: 
294; Fage, 1960:20-21. 
This is the first record of this species from 
Pacific North America. Two individuals were 
taken at depths of 360 and 520 m. Earlier work 
suggests a migration toward the surface at 
night. 
Streetsia challenged Stebbing 
Streetsia pronoides Bovallius, 1890:34, pi. 
Ill, figs. 7-12, p. 23, fig. 9, p. 35, fig. 62; 
Pirlot, 1938:360; Hurley, 1956:18-19. 
