NO. IO PHYLOGENETIC STUDY OF RECENT CRINOIDS CLARK 49 



2. Side- and covering-plates rudimentary (majority). 



1. All of the pinnules beyond the oral provided with ambulacral 



grooves (majority). 



2. Some or all of the pinnules on certain arms without ambu- 



lacral grooves (minority). 



General 



1.' Skeleton composed of more than a million ossicles (minority). 

 2. Skeleton composed of less than a million ossicles (majority). 



APIOCRINIDiE 



Calyx 



2. Calyx forming a platform upon which the viscera rest more or 



less supported by the arm bases. 



2. Calyx reduced by the eversion and imbrication of the calyx plates. 



1. Basals present. 



1. Five basals. 



1. Basals separate. 



1. Five radials. 



2. Interradials absent. 

 2. Anal x absent. 



2. Interbrachials absent. 



Column 

 1. Entire column present. 



1. Column jointed. 



2. Column not composed of short cylindrical ossicles with radial 



crenellae. 



1. Column composed of a single type of columnals, without a 



proximale or nodals (half). 



2. Column including modified columnals, a proximale or nodals 



(half). 



1. Column terminating in an expanded terminal stem plate. 



2. Radicular cirri absent. 



1. Cirri absent (half). 



2. Cirri present (half). 



Arms. 



2. Arms dividing one or more times, with IBr series. 



1. Arms with IBr series in which the outer element is axillary. 



2. The first bifurcation is on the second post-radial ossicle. 



