Orpinomyces intercalaris, a new species of polycentric anaerobic fungu
s from the rumen of cattle is described and illustrated. The zoospore
germinates to produce rhizomycelium which develops mostly intercalary
sporangia. The zoospore cyst is persistent and after germination remai
ns as an empty structure attached to the rhizomycelium. It is very dis
tinct during the early developmental stages of the rhizomycelium. Spor
angia are globose to subglobose. Zoospores are polyflagellated.