Vannellidae tend to be flattened and fan-shaped during motion, although some are long and narrow, and have a prominent clear margin at the anterior. In most amoebae, the endoplasm glides forward through the center of the cell, but vannellids undergo a sort of rolling motion with the outer membrane sliding around like a tank tread. These amoebae are usually 10-40 μm in size, but some are smaller or larger.
Vannellidae are surrounded by an outer covering called the glycocalyx, which is generally 10-20 nm across, though the thickness varies among species. In some species, a layer of hair-like filaments called glycostyles protrudes from the glycocalyx.
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- "Family Vannellidae Bovee, 1970". Microworld. Retrieved 4 July 2016.