434 
Aug. F. Foerste 
{R) correspond to rays 4 and 5, and the first branches of the 
left primary ray (L) correspond to rays 1 and 2, using these 
numbers in dextral order, as heretofore. In the following lines 
the terms left posterior, left anterior, anterior, right anterior, and 
right posterior will be used to express the homologies of the rays 
here indicated. 
The first dichotomous branching of the anterior ray takes 
place 2 mm. from the center of the oral area. The left and right 
branches of the anterior ray bifurcate again at distances of 3.5 
and 4 mm. respectively from the first fork, the secondary branches 
( s) not exceeding 2.5 mm. in length. 
Rays Nos. 1, 2, 4, and 5 bifurcate dichotomously (a, p) at dis- 
tances of 2.3 to 2.6 mm. from their origin at the ends of the left 
and right primary rays, most of the branches varying in length 
Fig. 1. Diagram of ray system of T hresherodiscus ramosa. A, L, R, anterior, 
left, and right primary rays. 1, 2, 3, 4, 5, left posterior, left, anterior, right, and 
right posterior rays; Z, r, left and right branches of anterior ray; a, p, anterior and 
])osterior branches of rays 1, 2, 4, and 5. 
from 3 to nearly 4 mm. The posterior interambulacral area 
contains the anus, on the side nearest the right posterior ray, as in 
other species of the Agelacrinidae. This posterior interambulacral 
area is of oval form, 4.5 mm. in width and nearly 7 mm. in length, 
following the curvature of the theca. The posterior branch of 
the right posterior ray, bordering the right posterior outline of the 
anal interambulacral area, appears to branch a second and third 
time, at distances of 2 and 4.5 mm. from the first fork of this ray, 
and similar forking may take place on the left posterior side of 
this anal interambulacral area, but the evidence for this is not 
perfectly clear. 
