406 



ZOOLOGY 



SECT. 



The aboral side of the disc is occupied by a large, flat, pentagonal 

 ossicle, the centro-dorsal ossicle (Fig. 331, c ; and Fig. 334, CD), 



syz cir 



FIG. 331. Aboral view of Antedon. c. ccntro-dorsal ossicle; cir. cirrus; /J,i R,~ R,3 the three 

 radial plates of one column ; syz. syzygy or articulation. (After MacBride.) 



bearing on its outer surface a number of little cup-like depressions, 

 with which the bases of the cirri are connected. The cirri (tirr) 



Fie. 332. Antedon, mal (upper) surface of the central disc. an. anus ; mo. mouth. 



(Krnni \ n-t and .lung.) 



consist each of a row of slender ossicles, covered, like all the rest 

 of the animal, with epidermis, and connected together by means 



