An order of Echinacea with a camarodont lantern, smooth or sculptured test, tubercles imperforate or perforate (and usually crenulate), ambulacral plates of diademoid or echinoid type, and branchial slits which are usually shallow. The order includes a long phylogenetic series in which the original characters change considerably so that a concise but exact diagnosis is not possible. Following is an evolutionary summary of the three included families. (1) The Glyphocyphidae, known only from the Cretaceous and Eocene and probably ancestral to the other two families, were small forms with a sculptured test, perforate crenulate tubercles, and diademoid ambulacral plates. Their sculptured test links them with (2) the Temnopleuridae whose tubercles, however, are imperforate, though usually crenulate. This family arose in the Cretaceous and abounds today, especially in the tropics, on strandlines. Most of the order, so far, had shallow branchial slits, but transitional forms link them with (3) the Toxopneustidae, Tertiary and extant forms where the slits are deep and the sculpture tends to vanish. At the same time, the tubercles become imperforate and noncrenulate and the ambulacral plates change to the echinoid type.