Petalosticha

Petalosticha, a. term applied by Haeckel to one of his two divisions of the Echinoidea or Sea urchins. It includes those in which the tube feet of one part of the ambulacra [Echinoidea] are specialised to serve for respiration; this part of the ambulacrum is generally expanded and so described as petaloid. The group is, however, now broken up into three: the Clypeastroidea, Cassiduloidea, and Spatangoidea.