The
heterotrichs are a class of
ciliates. They typically have a prominent adoral zone of
membranelles circling the mouth, used in locomotion and feeding, and shorter
cilia on the rest of the body. Many species are highly contractile, and are typically compressed or conical in form. These include some of the largest
protozoa, such as
Stentor and
Spirostomum, as well as many brightly pigmented forms, such as certain
Blepharisma.