102 SMITHSONIAN INSTITUTION 



Miller for the first), including among the Tessellata the principal representa- 

 tive genera of the present Flexibilia, Taxocrinus, Lecanocrinus, Forbesiocrinus 

 and Ichthyocrinus, which had in the meantime been established. 



In 1879 von Zittel x also took up the Mullerian families, — Tessellata, 

 Articulata and Costata, ranking them as suborders of the Crinoidea. None of 

 these authors, however, had given a clear definition of the chief diagnostic 

 character of the Articulata, and it remained for P. H. Carpenter to do this in 

 the " Challenger " Report on the Stalked Crinoids, pp. 145, 146, where he said 

 " the name-giving difference between the Articulata and the Tessellata is re- 

 duced to a supposed difference in the mode of union of the first radials with 

 the joints which they bear." 



In 1877 Wachsmuth, 2 in a profound analytical study of their structure, laid 

 the foundation for the general classification of the crinoids which in its essen- 

 tial features has been maintained in our joint and several works ever since. 

 He distinguished among' the Paleozoic crinoids three general plans of struc- 

 ture: The Taxocrinus plan (Taxocrinidae) ; the Cyathocrinus plan (Cyath- 

 ocrinidae) ; and the Actinocrinus plan (Spheroidae). These were elaborated 

 in our Revision of the Palaeocrinoidea, 1 879- t 886, under the respective corre- 

 sponding divisions Articulata, Inadunata (Larviformia plus Fistulata), and 

 Camerata, differentiated by the mode of union between the calyx plates, and 

 the condition of the arms, whether free above the radials or partly incorporated 

 into the cup. The Articulata were treated under a single family, the Ichthy- 

 ocrinidae. 



In our Monograph of the North American Crinoidea Camerata, 1897, 3 

 we adhered to the same divisions, with a change, however, in regard to the 

 Articulata, which was made to include not only the Paleozoic Ichthyocrinidae 

 under the subdivision Articulata Impinnata, but the Mesozoic and Recent 

 Apiocrinidae and Comatulae, as Articulata Pinnata. This arrangement was 

 partly based upon the idea that the growth of the stem in these forms pro- 

 ceeded by the interpolation of new ossicles beneath the top columnal instead of 

 next to the calyx; so that, as there expressed, the "top stem-joint is not the 

 youngest joint in the stem." It has long been evident to me that too much 

 importance was attached to this supposed feature, which was largely hypo- 

 thetical as to Paleozoic forms, and the existence of which as a fixed character 

 is disproved by my subsequent observations on some of the very forms in which 

 it was thought to be most prominent. 



Von Zittel in his Grundziige der Palaeontologie, 1895, adopted in prin- 

 ciple the classification of Wachsmuth and Springer in regard to the Paleozoic 



1 Handbuch d. Palaeontologie, p. 341. 



2 Internal and External Structure of Palaeozoic Crinoids, Amer. Jour. Sci., vol. 14, Aug. 1877, pp. 184-6. 

 a See pp. 150 et seq. 



