This website uses cookies to ensure you get the best experience. Learn more
are either incorporated in, or pressed below, the tegmen by interambulacrals; all thecal plates united by suture, somewhat loose in the earliest forms, but speedily becoming close, and producing a rigid theca; mouth and tegminal food-grooves closed; arms pinnulate.
All the Palaeozoic representatives have non-pinnulate arms, while the Mesozoic and later forms have them pinnulate.
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.