age similar to that of Simojovel, Portugal and Jolpabu- 
chil. Thus, available information suggests that the pres- 
ent samples represent a geologically short time interval. 
DETERMINATION OF RHIZOPHORA POLLEN 
Preparation Procedures 
The pollen samples were prepared by techniques modi- 
fied from various standard sources (Faegri and Iversen, 
1964; USGS Prep. Proc., 1960; Brown, 1960) in a 
manner found suitable in the treatment of sediments of 
this type in other investigations at the Paleobotanical 
Laboratories of the Botanical Museum of Harvard Uni- 
versity. Samples were first disaggregated by soaking in 
distilled water and by gentle grinding in a mortar with 
a pestle. The major portion of calcareous material was 
removed with 10% HCl; then lignin was removed by 
bleaching in acidified 7% NaClOeg. Larger quartz grains 
and other heavy minerals were removed by heavy-liquid 
separation in a solution of ZnBr2 in 10% HCl at a speci- 
fic gravity of 2.2. Finer silicious material was dissolved 
by overnight soaking of the sample in concentrated HF, 
followed by washing in HCl] to minimize silica gel for- 
mation. The samples were acetolysed to remove remain- 
ing cellulose, and mounted in glycerin Jelly. 
The fossil pollen types were identified by comparison 
with modern pollen in the Harvard Pollen Collection. 
Additional modern samples prepared for this study were 
treated by standard methods used for this collection: 
i1.e., treatment in hot 10% KOH followed by acetolysis 
and mounting in glycerin jelly. 
Modern Rhizophora pollen 
The genus Rhizophora was monographed by Salvoza 
in 1936, and was reviewed by Hou in 1960. Salvoza 
recognized R. Mangle L. and R. samoensis (Hochr. ) 
[ 297 | 
