250 PROCEEDINGS OF THE ACADEMY OF [1879. 



Posterior side = the anal side of the body. 



Anterior side = the side opposite the anal area. 



Bight or left = viewed from the posterior side. 



Rays = the whole collective succession of plates from the first 

 radial up. 



Free rays = radial extensions of the body unconnected b} r inter- 

 radial plates. 



Arms = radial extensions or branches from the body with a fur- 

 rOw on the ventral side. 



Pinnules = small, jointed, solid appendages, alternately arranged 

 along the arms. 



Tentacles = soft prehensile organs along the ambulacral furrow 

 of the arms and pinnules. 



Ambulacral furrow = groove on the ventral side of the arms and 

 pinnules, containing ambulacral canal and food passages. 



Proximal plates = those next to the column. 



Underbasals = the second ring of plates below the radials, here- 

 tofore called " basals" = pelvis of European authors. 



Basals = the first ring of plates below the radials, interradially 

 disposed, equivalent to " subradials" and " parabasals," botli 

 of which terms are discontinued by us. 



Radials all the plates of the body above the basals, radially 

 situated. 



Primary radials = those in the rays below the first bifurcation. 



Secondary radials = those between the first and second bifurca- 

 tion. 



Tertiary radials = those between the second and third bifurcation 

 (and so on up to the arms). 



Brachials = free radial plates supporting the arms. In our former 

 descriptions we have used the term " brachials" for that series 

 of radial plates within the body walls which leads to an arm 

 opening following Hall and others. Finding, however, that 

 this term has been previously applied to the " free radials" by 

 Johannes Miiller, and has been adopted by Roemer, Schultze, 

 and the zoologists generally, we propose to discontinue it as 

 applied to the former plates, which hereafter will be desig- 

 nated simply as radials of their respective orders. 



Interradials = plates between the rays and forming a part of the 

 body. 



