70 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



a. Primary anteroposterior axis. In the endocyclic comatulids 

 the axis passing along the anterior arm and continued through the 

 mouth and anal tube, leaving the animal in the center of the posterior 

 border of the anal area, divides it into two exactly similar halves 

 (see figs. 22-28, p. 69). 



b. Secondary anteroposterior axis. In such of the exocyclic 

 comatulids as have an interradial mouth, situated on the edge of the 

 disk between the bases of the anterior and right anterior rays the 

 anteroposterior axis which divides the annual into two bilaterally 

 equal halves passes through the middle of the interambulacral area 

 between the anterior and right anterior arms, through the mouth, 

 through the anal tube, and along the median line of the left posterior 

 ray (see figs. 26-28, p. 69, and pp. 152-161). 



(2) Dorsoventral axis. This axis passes through the dorsal pole and 

 through the center of the disk, being at right angles to the plane in which 

 the arms lie when extended horizontally. 



(3) Longitudinal axis. In speaking of the arms individually this 

 axis refers to the mid line of the arms; it is occasionally used in reference 

 to the pinnules or to the cirri. 



Azygous tentacle. The median tentacle of a tentacle group; usually the term 

 refers to the first tentacle which is formed in the larva (see fig. 543, pi. 4.) 



B. 



Basal. See Basals. 



Basal bridge. A narrow rounded ridge or rod connecting the inner ends of the 

 basal rays; the five basal bridges form a pentagon within which is seen the 

 rosette (see figs. 424-426, p. 321, 447-449, p. 353, 454, p. 355, 459-463, p. 357, 

 and 479, 480, p. 363, and pp. 324, 335). 



Basal cirrals. The one, two, three, or four very short cirrus segments immediately 

 adjacent to the centrodorsal (see fig. 4, p. 63, and p. 276). 



Basal fold. The incurved edge of the basal grooves, which is applied to the basal 

 ray. 



Basal grooves. The grooves on the dorsal surface of the radial pentagon which 

 lodge the basal rays ; they occur on the lines of suture between the radials (see 

 figs. 229-233, p. 247, 236-242, p. 249, 243-249, p. 251, 256-258, p. 255, and 

 pp. 236-238,370). 



Basal pentagon. The Radial pentagon. 



Basal rays. Prismatic calcareous rods of secondary origin developed in the basal 

 grooves between the radial pentagon and the centrodorsal; their inner ends 

 are usually connected with the rosette, and by basal bridges with the inner ends 

 of the adjacent basal rays (see figs. 9-12, p. 65, 97, p. 159, 208-215, p. 241, 

 227, p. 245, 229-233, p. 247, 416-427, p. 321, and 447-451, p. 353, and pp. 

 326-330). 



Basal ring. A structure formed by anchvlosed basals which show no trace of the 

 interbasal sutures (see figs. 3, p. 62, and 134, p. 203). 



Basal star. The five basal rays, plus the five connecting basal bridges (see figs. 

 447-451, p. 353, and pp. 324, 325). 



