Thalassicollida
in zoölogy, a family of Radiolaria. The animals consist of structureless cysts containing cellular elements and protoplasm, surrounded by a layer of protoplasm giving off pseudopodia, which commonly stand out like rays, but sometimes run into another, and so form networks. The best known genera are Thalassicolla, Sphærozoüm, and Collosphæra. They are all marine, being found floating passively on the surface of most seas, and vary in size from an inch in diameter downward.