420 
PACIFIC SCIENCE, VoL XIX, October 1965 
SUMMARY 
1. A total of 400 specimens of Gnathophausia 
were studied from the Seripps Institution of 
Oceanography’s 1950-53 collections made with 
the Isaacs-Kidd Midwater Trawl, In the east- 
ern Pacific Ocean, and four species were Identi- 
fied: (a) G. ingens: 204 specimens ranging in 
size from 25 to 139 mm body length (not in- 
cluding the rostrum ) , taken from a depth range 
of 274-3914 m, with an average depth of cap- 
ture of 1100 m; (b) G. gigas: 66 specimens 
ranging in size from 21 to 142 mm body length, 
taken from a depth range of 603-4883 m, with 
an average depth of capture of 2100 m; (c) G. 
gracilis: 128 specimens ranging in size from 22 
to 115 mm body length, taken from a depth 
range of 732-3914 m, with an average depth 
of capture of 1600 m; (d) G. zoea: 2 speci- 
mens, a female of 48 mm body length and a 
male of 4-1 mm body length, taken from a depth 
of 0-1016 m. 
2. The geographical distribution of G. gigas, 
a colder water form, in the eastern Pacific is 
more northerly (20°-60°N) than is that of G. 
ingens and G. gracilis, which occur in warmer 
waters and exhibit a more tropical distribution, 
particularly G. gracilis. 
3. Of the 128 specimens of G. gracilis col- 
lected 99 were found north of the Tropic of 
Cancer in the eastern Pacific Ocean, an area 
where they had rarely been found previously. 
4. G. ingens was found consistently deeper 
in daylight hauls than in hauls taken at night, 
possible evidence for nocturnal vertical migra- 
tion in this species. No evidence for this phe- 
nomenon is shown for G. gigas or G. gracilis. 
5. Among the specimens of G. gracilis 6 were 
greater than 100 mm in body length, the larg- 
est measuring 115 mm. All are larger than any 
G. gracilis individuals previously described. 
6. A mature female specimen of G. gigas 
measuring 105 mm in body length and having 
a well developed marsupium is described. 
7. A parasitic ellobiopsid flagellate, Amallo- 
cystis fasciatus, is reported from 2 specimens of 
G. ingens and 1 specimen of G. gracilis taken 
from the eastern Pacific Ocean. 
ACKNOWLEDGMENTS 
This study was undertaken at the Seripps In- 
stitution of Oceanography in 1955, while I was 
studying under a National Science Foundation 
Pre-Boctoral Fellowship under the guidance of 
Dr. Martin W. Johnson. 
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