Tetraplatia — Hand 
335 
from about 23° to 30° S. in the western At- 
lantic (east and south from Rio de Janeiro, 
Brazil). Komai (1939) reported this animal 
from the Pacific for the first time. His report 
concerned four specimens taken in May at 
Susaki, Japan. Carlgren (personal communi- 
cation) has informed me that he also has 
specimens from the western Pacific collected 
Fig. 2. Section through a lappet and statocyst, oral 
surface uppermost. 
by the Dana expedition. The present report 
concerns the occurrence of T. volitans in the 
eastern Pacific. A total of 211 specimens has 
been found in 76 different net hauls from 44° 
N. to 5° S. and as far west as 131° W. The 
most northerly specimen was collected at 44° 
12' N., 128° 37' W.; die most southerly at 
5° 04' S., 95° 56' W. and the most westerly 
at 39° 38' N., 131° 36' W. Of the total spec- 
imens from the Pacific Ocean 167 were col- 
lected during the course of routine sampling 
by the Scripps Institution of Oceanography 
as part of the California Cooperative Sardine 
Research Program and also on its expedition 
"Shellback” to the eastern tropical Pacific. 
The remaining specimens (44) were collected 
in Monterey Bay, California, by personnel of 
Hopkins Marine Station during the course 
of their work on NC-ONR# 25127. Figure 4 
shows the areas from which the specimens 
from the eastern Pacific were collected where- 
as Figure 5 indicates the world wide nature 
of the distribution of T. volitans. No specimens 
have been reported from the Arctic or Ant- 
arctic regions, nor as yet from most of the 
southern, and western Pacific. 
The early workers on Tetraplatia commented 
but little upon its way of life. All the early 
specimens seem to have been taken in super- 
ficial net hauls and usually at night. Viguier 
(1890) thought they occurred "en petites 
troupes” and that they were the pelagic phase 
of a fixed or benthic animal. He points out 
that he did not find these animals associated 
with the truly pelagic (oceanic) forms. Carl- 
gren (1909) was of the opinion that the tetra- 
platians were holoplanktonic. Dantan (1925), 
however, basing his conclusions on his ob- 
servations of living animals, their movements 
and behavior, and on the spotty occurrence 
of these animals believed that they occur only 
accidentally in the plankton. He thought that 
they were not truly pelagic and that they lived 
near the bottom in rocky areas since net 
samples near sandy and muddy bottoms did 
not contain them. Dantan also disagreed with 
Viguier to the extent that when he (Dantan) 
found Tetraplatia it was in typical plankton 
assemblages. Leloup (1935) has taken an al- 
Fig. 3. Oral view of an expanded and flattened 
lappet. 
together different point of view on the mode 
of life of this animal, and one to which I 
subscribe as will be seen in the observations 
and discussions to follow. He points out that 
the animals seem to be taken either in deep 
hauls during the day or in surface hauls 
during the night and suggests the animal must 
undergo a diurnal migration, coming to the 
