Sarcocystis infections in mule deer (Odocoileus hemionus) in Montana and the descriptions of three new species.

Four structural types of sarcocysts of Sarcocystis were found in skeletal muscles of mule deer in Montana. Type I sarcocysts were thin walled (1 to 3 micron) and belonged to S hemionilatrantis. Types II to IV sarcocysts were thick walled (2 to 10 microns) and new names were proposed for them. Type II sarcocysts with long villar projections were named S hemioni. Type III sarcocysts with club-shaped villi of uneven thickness were named S youngi. Type IV sarcocysts with walls of uneven thickness and containing hair-like protrusions were named S americana.