No existing classification of the Asterida is satisfactory even for the recent forms, still less when the older fossils are considered. A separation of the latter as Palasterida, because of their alternating ambulacrals, from the recent Euasterida with opposite ambulacrals, is now discarded and an attempt made to arrange the Palasterida in divisions originally established for Euasterida. Those divisions fall under three schemes. C. Viguier has divided the starfish into: _Astéries ambulacraires_, with plates of ambulacral origin prominent in the mouth-skeleton, pedicellariae stalked, and straight or crossed, podial pores usually quadriserial; _Astéries adambulacraires_, with adambulacrals prominent in the mouth-skeleton, pedicellariae sessile, and forcipiform or valvular, podial pores usually biserial. Perrier, at first laying greater stress on the nature of the pedicellariae and afterwards on the form of the mouth-skeleton, has gradually perfected a scheme of five orders: (1) _Forcipulata_, with pedicellariae stalked, and straight or crossed; (2) _Spinulosa_, with pedicellariae sessile and forcipiform; (3) _Velata_, with membraniferous spines; (4) _Paxillosa_, pedicellariae represented by an ossicle of the test and the spines covering it, the whole forming a paxilla; (5) _Valvata_ or _Granulosa_, with pedicellariae sessile and valvular or salt-cellar shaped. A more widely accepted scheme is that of W.P. Sladen, who divided the Euasterida into two orders; (1) _Phanerozonia_, with marginals large and highly developed, the supero-marginals and infero-marginals contiguous, with papulae confined to the dorsal surface, with ambulacrals well spaced and usually broad, adambulacrals prominent in the mouth-skeleton, with pedicellariae sessile; (2) _Cryptozonia_, with marginals inconspicuous and somewhat atrophied in the adult, the supero-marginals separated from the infero-marginals by intercalated plates, with papulae distributed over the whole body, with ambulacrals crowded and narrow, either ambulacrals or adambulacrals prominent in the mouth-skeleton, with pedicellariae stalked or sessile. We give here a list of the families separated into Sladen's orders and grouped under Perrier's divisions, extinct families being marked [+]. [Illustration: FIG. 16.--Section across the arm-skeleton of a Phanerozonate Asterid, _Astropecten_. a, Ambulacral plates. b, Adambulacral plates. c and d, Inferior and superior lateral plates. e, Dorsal plates with paxillae. Certain supra-ambulacral plates, which also exist, are not shown.]