A treatise on zoology . research for a large amount of confirmatory evidence. ^ Zle Oralia mit den Radialien verhindcnden Plattchen. 142 THE CRINOIDEA The Classification here adopted keeps accejjted terms so far aspossible, but the distribution of the groups is very different from thathitherto accepted. Dividing all Crinoidea into Mo^OCYCLICA andDiCYCLiCA, we trace in each order a gradual and to some extent parallelmodification, here and there diverging in somewhat similar the simplest forms in each order are Inadunata, with free distinctarms, and pass from a Larviform stage, w
A treatise on zoology . research for a large amount of confirmatory evidence. ^ Zle Oralia mit den Radialien verhindcnden Plattchen. 142 THE CRINOIDEA The Classification here adopted keeps accejjted terms so far aspossible, but the distribution of the groups is very different from thathitherto accepted. Dividing all Crinoidea into Mo^OCYCLICA andDiCYCLiCA, we trace in each order a gradual and to some extent parallelmodification, here and there diverging in somewhat similar the simplest forms in each order are Inadunata, with free distinctarms, and pass from a Larviform stage, with simple tegmen, to a Fistulatestage, with more complex anal tube and tegmen. At an early period(? Cambrian) in the history of the Monocyclica, the Camerate modification,viz. rigid incorporation of brachials in cup and ambulacrals in tegmen,affected a few forms, and thus arose Monocyclica Camerata. At a laterperiod (Silurian) was a repetition of this modification, but one affecting the MONOCYCLICA. DICYCLICA. inadunata k Cambrian. (LAIIVIFOBMIA). Oidovician. Silurian. Devonian. Carboniferous. Permian. Tha». JuraMic Cretaceous. Tertiary. Recent. cup to a far less extent, and resulting chiefly in a solid tegmen and biserialarms ; thus arose the Monocyclica Addnata (or Platycrinoidea), whicheven Wachsmuth and Springer find a difliculty in placing with theCamerata. two highly siacialised brunches died out before theclose of the Palaeozoic epoch, the Adunata outliving the Camerata ; butthe simpler Tnadunatc, formn continiud, and ivaohed a high degree in their Jurassic descendants, to which the living IliitHrinuais closely related. The Dicyclica Inadunata similarly gave otf theDiCYCLiCA Camkkata, whicli persisted only a little less long than theirmonocyclic convergents. The dicyclic Crotalocrinidae of the Silurianare curiously parallel to the Monocyclica Adunata, but it is not worthwhile to separate! them from the tyj)iral Inadunata. About the sa
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