cycloidei

from The Century Dictionary.

• In L. Agassiz's system of classification, the fourth order of fishes, including those with cycloid scales—that is, scales of the usual type, marked with concentric rings and not enameled or pectinated.

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Zoöl.) An order of fishes, formerly proposed by Agassiz, for those with thin, smooth scales, destitute of marginal spines, as the herring and salmon. The group is now regarded as artificial.