Each radial is the first, or most proximal, ossicle of a ray . Each ray consists of a series of ossicles, usually branched, that extends outward from the body, and bears an open ambulacral groove bordered by small fingerlike tube feet .
Ossicles following the radials are brachials .
Each axil has two distal articular faces and may thus bear two unbranched arms , two additional brachitaxes, or one of each. In unbranched rays, the arms extend from the radials. Rays and their various branches carry extensions of coelomic, nervous and water vascular systems. Branching patterns are often diagnostic at generic and, sometimes, family levels. In all living crinoids and many fossil species, each arm bears smaller, segmented, unbranched appendages, pinnules , arranged in alternating series on either side of successive brachials.