IIO SMITHSONIAN INSTITUTION 



pendent rank of this group, that it has an open mouth and exposed food- 

 grooves like the Recent crinoids. 



In von Zittel's Handbuch der Palaeontologie, 1879, the Taxocrinidae and 

 the Ichthyocrinidae were listed simply as two of 26 families under the suborder 

 Tesellata. But in his Grundziige der Palaeontologie, 1895, he adopted in sub- 

 stance the primary divisions of Wachsmuth and Springer, substituting, how- 

 ever, for their Ichthyocrinidae the obvious and appropriate name suggested by 

 Wachsmuth's original definition, the Flexibilia. 



In 1888 Wachsmuth and Springer 1 discovered the tegmen, or vault, in a 

 specimen of Taxocrimis intermedins, in so perfect a condition as to leave no 

 doubt whatever as to the complete differentiation of this type from that of the 

 other groups of Paleozoic crinoids. Consistently with the flexible calyx, it 

 proved to have an integument of pliant perisome, with exposed food-grooves 

 passing over it between parted oral plates into a central open mouth. This 

 discovery thoroughly fixed the status of the order now called Flexibilia as an 

 independent group, and it has been since confirmed by the discovery of similar 

 tegmens in another species of Taxocrimis, and in Onychocrinus, Synerocrinns, 

 Homalocrinus and Pycnosaccns, representatives of three of the families into 

 which the order is divided. 



Induced by this unexpected anatomical similarity to the Recent crinoids, 

 we undertook in the paper last cited to attach the name Articulata to this group, 

 and in our later work on the Crinoidea Camerata we proposed to include within 

 it the Apiocrinidae and Comatulae as Articulata Pinnata, while the non- 

 pinnulate paleozoic members would constitute another section called Articulata 

 Impinnata. The use of the name " Articulata " in this sense was admittedly 

 questionable, and it was suggested that " Articulosa " of Jaekel might be 

 adopted as an alternative. The text of our work was completed in 1894. 

 Owing to the protracted illness of Wachsmuth, and the engrossing business 

 cares of the present writer, we did not keep in touch with current literature 

 while it was passing through the press, and therefore the peculiarly apt term 

 " Flexibilia," employed by von Zittel in 1895, was overlooked. Had it been 

 known to us, the text would have been corrected in the proofs so as to utilize it. 



In the Lankester Treatise on Zoology, 1900, Bather adopted the term 

 "Flexibilia" as equivalent to the Articulata of Wachsmuth and Springer, not 

 Miiller, and with it the two subdivisions Impinnata and Pinnata. He arranged 

 the Impinnata under five families: Ichthyocrinidae, Gazacrinidae, Tax- 

 ocrinidae, Dactylocrinidae and Sagenocrinidae. As to these he said: "The 

 genera seem to merge into one another, and are as yet too ill-defined to be 

 grouped into families on a sure genetic basis" (p. 187). His Gazacrinidae 



1 Discovery of the Ventral Structure of Taxocrimis, Proc. Acad. Nat. Sci. Philadelphia, for li 

 pp. 337-363- 



