CLASSIFICATION IC>5 



facts may thus be fairly marshalled as material for future discussion by some 

 one of the status and relationship of the subdivisions of the Crinoidea. In the 

 meantime, in view of the widely divergent results attained by the application 

 of phylogenetic principles in the two later classifications, I feel content to stand 

 upon the general features of the plan - of Wachsmuth and Springer regarding 

 the Paleozoic crinoids, with some modifications in detail suggested by newly 

 acquired knowledge; returning, however, to the Articulata of Miller and 

 Muller for the Recent and most of the Mesozoic crinoids. Accordingly we 

 shall have the following table for expressing the — 



PRIMARY DIVISIONS OF THE CRINOIDEA 



Crinoids with a rigid calyx in which the lower brachials are to a varying extent 

 firmly incorporated into the dorsal cup, being rendered fixed and immovable by 

 union either with dorsal or ventral structures. Plates of the calyx united by close 

 suture. Mouth and calyx food-grooves chiefly subtegminal. Subject to modifica- 

 tion as to either character in transition "forms. Arms pinnulate. 



Order Camerata. 



Crinoids with a flexible calyx in which the lower brachials are loosely incor- 

 porated into the dorsal cup either by lateral union with each other, by means of 

 interbrachials, or of a skin studded with calcareous particles. All plates beyond the 

 radials united by loose suture, and more or less movable. Mouth and tegminal food- 

 grooves exposed. Arms non-pinnulate. Order Flexibilia. 



Crinoids with rigid calyx in which the brachials are free (or sometimes loosely 

 connected) above the radials. Plates of the calyx united by close suture. Mouth 

 sub-iegminal ; food-grooves supra-tegminal, but may be closed by fixed ambulacral 

 plates. Arms pinnulate or non-pinnulate. Order Inadunata. 



Crinoids in which the mode of union of the radials with the plates they bear is 

 by. complete muscular articulation, and in which are combined certain additional 

 characters stated below. Arms pinnulate. Order Articulata. 



The Camerata were a highly specialized group, confined to the Paleozoic, 

 and becoming extinct in the Lower Coal Measures. Within this group occurred 

 various modifications of base, anal structures, and arms, affording criteria for 

 the sharp differentiation of families, but all subordinate to the general type of 

 a solidly enclosed calyx, combined with the absence of, or a restricted, move- 

 ment of the brachials upon the radiials. There is, of course, in some forms 

 more or less of a tendency to modification of these characters in the direction 

 of other groups, as among the Platycrinoids, where there is often but slight 

 incorporation of the brachials, or none at all, in the dorsal cup. In these cases, 

 however, there is usually a very definite restriction in the mobility of the 

 brachials upon the radials by means of rigid adambulacral and covering plates. 

 Any proposal for segregating the Platycrinoids and Plexacrinoids into an inde- 

 pendent group upon this character would be nullified by the many important 

 exceptions formed by cases in which the first brachial is completely incor- 



