During locomotion the cells are flattened and have a clear layer called hyaloplasm along the front margin. Some form slender subpseudopodia projecting outward from the hyaloplasm, but the cell mass does not flow into these as in true pseudopodia, and advances without a definite central axis as in the Tubulinea. They also lack distinctive features like shells and flagella, and are united mainly by evidence from molecular trees.