1912] Esterly: Copepoda of the San Diego Region 313 
TABLE 39 
Distribution of Pleuromamma abdominalis at the surface at night in 
two-hour periods 
Time of No. of hauls No. of hours No. of animals Frequency 
day Total Suecess. Total Success. Total Per hour Haul Hour 
p.m. A B Cc ) E ¥ G H 
a 6-8 30 2 20.0 2.4 45 2.2 i 12 
2. 8-10 8 4 44 2.2 254 58.8 50 50 
3. 10-12 1 1 2:8 2:8 14 5.0 100 100 
a.m. 
12-2 3 3 2.6 2.6 39 =: 15.0 100 =100 
2-4 8 3 12.0 3.0 12 1.0 37 25 
4-6 41 4 26.6 1.4 6 0.22 10 5 
60 
58 
[tea a a ea 
6-8 8-10 10-12 12-2 2-4 4-6 
P.M. A.M. 
Fig. 6. Pleuromamma abdominalis. Variations in numbers per hour at 
the surface at night. Data in table 39. 
The time of greatest abundance is from 8-10 p.m. (line 2), 
though the frequencies are greatest within the next four hours 
(lines 3 and 4). It seems that there is a sudden and marked 
rise to the maximum and a drop that is almost as abrupt. This 
species was found at the surface at temperatures ranging from 
