THE CRINOIDEA 141 



Jjotryocriniis, Encrinus, Uintacrinus, Crotalocri?ius, Cyathocrinus). The 

 Reteocrinidae (W. & Sp.) present us with the Articulate or Flexible stage 

 of the Camerata, and include both Dicyclica and Monocyclica. It is 

 reasonable to suppose that the monocyclic Melocrinidae, Calyptocrinidae, 

 Batocrinidae, and Actinocrinidae were derived from monocyclic ancestors, 

 whether Reteocrinidae or others, and that the dicyclic Thysanocrinidae 

 and Rhodocrinidae were derived from dicyclic Reteocrinidae and similar 

 forms. On the other hand, the Platycrinidae, and their descendants, 

 Hexucrinidae and Acrocrinidae, are closer to the Inadunata, and sprang 

 probably from monocyclic genera, independently and at a later period. 

 The Crotalocrinidae, which Wachsnmth and Springer now place in the 

 Camerata, are at any rate of totally different origin from all other Camerata, 

 and are intimately allied to Cyathocrinus and Gissocrinus among the 

 dicyclic Inadunata. 



Previous authors have attempted to make their classification serve as 

 a key to structure rather than as an epitome of descent. And the above 

 considerations suggest that Wachsmuth & Springer's system, though far 

 the best from an anatomical standpoint, is not the phylogenetic classifica- 

 tion sought by the modern biologist. 



A bold attempt at a phylogenetic classification is shortly to be brought 

 out by Jaekel. From his preliminary notice (1894) and subsequent 

 writings it appears that he separates the Camerata (W. & Sp.), under the 

 name CLADOIDEA, from the rest, to which he restricts the name CRINOIDEA. 

 The Crinoidea have radials, five arms with brachials, and ramuli (Jaekel, 

 supra), and anal plates connected with right posterior radial ; their origin 

 is from such a simple type as has been described above. The Cladoidea 

 originated independently from a many-plated cystid, in which numerous 

 arms produced as many rows of supporting plates (costalia) in the cup, not 

 homologous with radials and brachials ; the free costalia bear pinnulae 

 (Jaekel, supra). The resemblances between Cladoidea and Crinoidea are 

 admittedly great, but all to be explained comfortably by homoplasy and con- 

 vergence. The Crinoidea (Jaekel) are divided into : FISTULATA : the root- 

 group, with primitive, simple calyx ; including the generally accepted genera, 

 also Porocrinus, Crotalocrinidae, and Marsupites. LARVATA : essentially 

 the same as Larviformia (W. & Sp.), but supposed to be derived from 

 Fistulata, perhaps through Heterocrinidae. COSTATA : " arms give off 

 undivided, alternating side-branches, serving in part for reception of 

 gonads ; cup usually thin-walled and spacious, composed of a circlet of 

 large RR and a tripartite or fused base. No anal plates or tube ; tegmen 

 simple, of five 0, to which suboralia l may be added " ; Hybocrinidae, Hapa- 

 locrinidae, Plicatocrinidae, Hyocrinidae, Saccocomidae, Rhizocrinidae (?). 

 ARTICULOSA : the old Articulata, W. & Sp. non Miiller ; Lecanocrinidae, 

 Ichthyocrinidae, Taxocrinidae. ARTICULATA, Miiller non W. & Sp. : 

 derived from Fistulata not from Articulosa ; Encrinidae, Pentacrinidae, 

 Apiocrinidae, Eugeniacrinidae, Antedonidae. JaekePs proposals are here 

 alluded to in order that the student may understand the terms used in 

 his forthcoming finely illustrated work. They are valuable as suggesting 

 research for a large amount of confirmatory evidence. 



1 "Die Oralia mit den Radialien verbindenden Plattchen." 



