Perischoechinoida
Perischoechinoida (subphylum Echinozoa, class Echinoidea) A subclass of regular echinoids, without compound plates, in which the perignathic girdle is absent or of apophyses only, the teeth are grooved, and there are no gill slits or spheridia. The number of columns of plates in ambulacra and interambulacra is very variable except in Cidaroida. These echinoids first appeared in the Ordovician.
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except , ex·cept / ikˈsept/ • prep. not including; other than: they work every day except Sunday. • conj. used before a statement that forms an exception to o… Exception , exception •ashen, fashion, passion, ration •abstraction, action, attraction, benefaction, compaction, contraction, counteraction, diffraction, enacti… Euechinoidea , Euechinoidea (class Echinoidea) Sub-class of sea-urchins in which the normally rigid test is composed of five ambulacra and five interambulacra, each… Regular Sample , regular sample (systematic sample) One of a number of samples taken at regular intervals (e.g. by the use of regularly spaced quadrats along some env… Cryptodonta , Cryptodonta (phylum Mollusca, class Bivalvia) A subclass of bivalves most of which have thin, equivalve shells composed of aragonite. They have an am… irregular , ir·reg·u·lar / iˈregyələr/ • adj. 1. not even or balanced in shape or arrangement: her features were too irregular. ∎ occurring at uneven or varying…
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Perischoechinoida