endobranchiata

from The Century Dictionary.

• A group of regular Echinoidea, having the mouth and anus at opposite poles, the anus surrounded by the apical system of plates when they are present, and no external gills. It includes the orders Bothriocidaroida., Cystocidaroida, Cidaroida, Melonitoida, and Plesiocidaroida. Compare Ectobranchiata.