America. Here, behind the Rhizophora zone, the back- 
swamp vegetation is usually a mixed swamp forest type 
which forms a gradual transition to rain forest. In Mexico 
and some other areas of Central America, where hills 
come down to the shore, such a transition belt is usually 
narrow or absent. 
As previously noted, Hymenaea Courbaril today fre- 
quently occurs in habitats closely associated with man- 
groves along the Pacific coast of Central America. This 
has been observed by the senior author along the Guer- 
rero coast in Mexico and along the Osa Peninsula in 
Costa Rica. Lindeman (1953) also has reported H. 
Courbaril as occurring in Surinam on low sand ridges 
near the mangroves. 
The most significant present-day situation observed 
by the senior author that might represent possible site 
conditions like one of those in which the Chiapas amber 
could have been deposited occurs around Puerto Marques 
Bay, Guerrero, Mexico. Here, H. Courbaril is one of 
the dominant trees in a Tall-Medium Subdeciduous 
forest-type (Miranda and Hernindez-X, 1963) on the 
hills sloping either to the ocean or to bays (Plate X LI). 
Hymenaea occurs along rivers that enter the lagoons 
and also on sandy ridges that interdigitate into the lagoon 
(Plate XLI). These lagoons are fringed primarily by 
R. Mangle and on higher ground by Laguncularia race- 
mosa (Plate XLI). Hymenaea also may be found on 
dune and beach ridge vegetation along the coast in Guer- 
rero and Oaxaca. Around Puerto Marquez Bay, it is 
easy to visualize how resin from Hf. Courbaril would be 
deposited into the lagoon with fringing mangroves. A 
single severe flooding could wash away resin collected in 
the soil, and the stilt roots of Rhizophora offer an excel- 
lent mechanism to ‘‘trap’’ the resin. Also, resin may 
easily be transported down rivers that enter the bays and 
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