276 FIELD CoLuMBIAN MusEuM — Geo oey, VoL. II. 
Interbrachtal areas (1 Br.*): The plates in camerate crinoids sit- 
uated between the rays. 
Anal or posterior interradius (X. a.a.): The area situated between 
the right and left posterior rays and leading up to the anal opening. 
Basals (B): The circle of plates directly below the radials and alter- 
nating with them. Ina monocyclic base they join the column. 
Infrabasals (1 B): The first row of plates in a dicyclic base. They 
separate the basals from the column and are radial in position. 

Fig. 1. Diagram of a Monocyclic, Camerate Crinoid. 
Radtals (R): The first plate of each ray, usually resting on the ba- 
sals. In some families part of the radials are divided horizontally. The 
parts of these plates are called superradials (Rs) and inferradtals (Ri), 
respectively. 
Costals (C): Those plates of each ray extending from the radials, on 
which they rest, up to the first bifurcation. 
Distichals (D): All plates of each ray between the first and second. 
bifurcation. 
Palmers (P): All plates of each ray between the second and third 
bifurcation. Any plates of a higher order than these are called post- 
palmers. 
* The letters in parenthesis refer to those of Figs. 1 and 2. 
Fig. 2. Diagram of a 
Dicyclic Crinoid. 
