56 SMITHSONIAN MISCELLANEOUS COLLECTIONS "VOL. 65 



III. Disk 



The presence or absence of plating on the disk. 

 The presence or absence of orals. 



The condition of the orals, whether with or without upturned 

 edges. 



The central or excentric position of the mouth. 



IV. Arms 



The structure of the arms, whether a linear series of ossicles with- 

 out IBr series, or dividing one or more times, or with IBr series. 



The condition of the IBr 2 , whether axillary or not. 



The position of the first post-radial axillary, whether on the 

 second post-radial plate or beyond. 



The type of the union between the plates of the IBr series, whether 

 a suture (pseudo-syzygy) or a synarthry. 



The condition of the division series, including a definite or an 

 indefinite number of plates. 



The condition of the union between the radials and the arm bases, 

 whether or not the latter occupy the entire distal border of the 

 former. 



The equality or inequality in the length of the arms. 



The definite or indefinite termination of the arms. 



The presence or absence of ambulacral grooves on all the arms. 



V. Pinnules 



The prismatic or cylindrical form of the pinnules. 

 The presence or absence of differentiation of the proximal pinnules. 

 The development or non-development of side- and covering- 

 plates. 



The presence or absence of ambulacral grooves on all the pinnules. 



VI. General 

 The presence of more or less than a million skeletal elements. 



PLICATOCRINID^ 



I. Calyx 

 Five or fewer basals. 

 The individual occurrence, or fusion, of the basals. 



