Two new myxomycete species recorded from the semiarid lands of the Neotropi
cs are described. Crihraria fragilis sp. nov. is distinguished from all oth
er species of the genus by its unique spores, which have smooth bands arran
ged in longitudinal arcs, and by the minute sporocarps each with a deep cal
yculus and without a peridial net. Diderma acanthosporum sp. nov. has a uni
que combination of characters; these are a pseudoaethalioid fructification
with stalked sporocarps and depressed sporothecae, a calcareous, crustose e
xternal peridial layer, and large spores, paler on one side and with long s
pines. Comments on the distribution and ecology of these two species are in
cluded.