Definitions for "Acantharea"
The Acantharea are a small group of radiolarian protozoa, distinguished mainly by their skeletons. These are composed of strontium sulfate crystals, which do not fossilize, and take the form of either ten diametric or twenty radial spines. The central capsule is made up of microfibrils arranged into twenty plates, each with a hole through which one spine projects, and there is also a microfibrillar cortex linked to the spines by myonemes.