type pollen, and will be designated as R. Mangle-type.’ 
The second consists of pollen of R. racemosa-type and 
R. Harrisoni-ty pe and will be designated as Rhizophora- 
spp. In this group are included fossil Rhizophora grains 
present in very small quantities in several of the fossil 
samples which resemble those of RP. Harrisoni but which 
are not completely distinct from somewhat crumpled 
grains of FR. samoensis. Since these grains occur con- 
sistently together with high percentages of R. racemosa- 
typeand R. Harrisonu-type, and decrease in percentage 
as PR. Mangle-type increases, their affinity is probably 
with the former group. The category ‘‘ Rhizophora aftini- 
ty uncertain’’ was established to include grains which, 
due to poor preservation or unfavorable orientation, 
could not be placed with certainty in one of the major 
‘ategories. 
It is not proposed in this study to attempt a rigorous 
statistical treatment of the observed Rhizophora pollen 
nor to identify minor components of this pollen flora. 
An initial investigation of the slides indicated that a 
count of 200 grains per sample was sufficient to suggest 
the major outlines of the vegetation and the relative 
frequencies of the most abundant pollen types. For this 
purpose, slides were scanned at 300. Final determina- 
tions were made at higher magnifications. The first 200 
identifiable pollen grains were recorded. Record was kept 
also of the relative percentages of pollen and fungal 
spores in each sample. Data concerning the relative 
abundances of different Rhizophora pollen types and of 
” Nomenclature of the fossil pollen follows the principles outlined 
by Zagwijn (1960), As summarized by Muller (1964, p. 35), these 
may be stated as follows: “‘If a fossil pollen type has been assigned 
to a given natural taxon, this expresses the author’s confidence in a 
high degree of probability for the identification. If, however, the word 
**-type’’ is added this means that the pollen type is known to occur 
also in a related taxon of the same rank.’’ 
[ 303 | 
