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), 



si/z cir 



Fig. 331.— Aboral view of Antedon. c. centro-dorsal ossicle ; dr. cirrus ; R, 1 R* R3 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 (cirr) 



Fig. 332.— Antedon, oral (upper) surface of the central disc. an. anus ; mo. mouth. 

 (From Vogt and Jung.) 



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

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



