CLASS III CRINOIDEA 227 



in pelagic forms, massive, and, except in (he pelagic forms, much reduced in size. 

 Radiais and arm-plates perforated hy separate dorsal canal. Base in most cases 

 adually or potentially dicyclic ; the infrabasals, and sometimes also the hasals, 

 heilig often atrophied, radically altered hy resorption and subsequent rehuilding, or 

 ahsent altogether. 



Proximal columnal always modified, usually enlarged, attached to the 

 calyx by close suture, to the columnal below it also by close suture (the 

 so-called stem-syzygy) ; but this pair of columnals in some forms, instead 

 of maintaining the original connection with the calyx, is separated from it 

 by varying intervals in the stem, or at least in its proximal portion. Union 

 between the plates of the dorsal cup is by close suture, between the radials 

 and the primibrachs by muscular articulation, and between the elements of 

 the primibrach series by non-muscular articulation. Eadials always in lateral 

 contact. Radianal and anal plates may be represented as such in the larval 

 stages, but never in the adult ; and the anal occasionally develops into a sup- 

 plementary radial, bearing a typical post-radial series indistinguishable from 

 those on the other radials. Arms uniserial and pinnulate, though the basal 

 pinnulation is often defective. No concavity in the apex of the dorsal cup 

 for the reception of the stem. Stem reduced to a single columnal in the 

 Comatulid division of this order. Lias to Recent. 



In the earlier German and English editions of this work, following the example 

 of previous European authors generally, the Mesozoic and Recent Crinoids (excepting 

 Marsupites, Uintacrinus, and perhaps Encrinus) were treated as a distinet group from 

 the Paleozoic under the name Articulata, proposed by J. S. Miller for the Apiocrinidae, 

 Encrinidae and Pentacrinidae, and extended by Johannes Müller to include the 

 Comatiüids. The chief characters relied upon to distinguish the order, viz. (1) «n 

 open mouth and food grooves, (2) a separate axial or dorsal canal perforating the 

 arms, were admittedly indecisive, considering that the first belongs eqiially to the 

 entire Paleozoic groiip Flexibilia, and the second is shared by a Devonian family and 

 several genera of the Inadunata. 



This evident inadequacy of the definition has led to various proposed Substitutes 

 for the plan, such as placing the Pentacrinidae under the Fistulate Inadunata, and 

 the Comatulids together with the Apiocrinidae, etc., as a subdivision (" Pinnata ") 

 under the Flexibilia. None of these has proved satisfactory ; least of all the last, 

 for the lack of any sufficiently definable connection between the so-called Pinnata and 

 the Paleozoic Flexibilia. The very pliant calyx of the latter recurs in the pelagic 

 Comatulids, Marsiqntes and Uintacrinus, and the close lateral union or partial 

 incorporation of lower brachials is found to some extent among the Apiocrinidae, 

 Pentacrinidae, and some Comatulids. But it has become increasingly evident that 

 the Flexibilia were a specialised group, derived from the Inadunata, and ending like 

 the Camerata with the Paleozoic. 



The only one of the primary divisions of the Crinoids that seems to have survived 

 is the Inadunata, the most generalised type, from which all the post-Paleozoic forms 

 are evidently descended. While, therefore, there is no valid ground for any such 

 divisions as Paleocrinoidea and Neocrinoidea, as proposed by Wachsmuth and Springer 

 and by Carpenter, but afterward abandoned, yet it cannot be denied that, with the 

 sole exception of the Triassic Encrinus, the known Crinoids of Mesozoic to Recent 

 times have an assemblage of features by which they are broadly distinguished from 

 their Paleozoic ancestors. And it is believed that this may be expressed under the 

 group Articulata as enlarged by Johannes Müller, distinguished not by any single 

 character peculiar to itself, but by the fact that a large numljer of characters belonging 



