fig. 2). The colour of Antedon is very variable. Some 

 specimens are of a deep reddish purple, uniformly 

 distributed over both disc and arms, but the majority are 

 clouded and spotted with rose, orange, and yellow tints. 

 The colouring matter is highly soluble in fresh water, 

 alcohol, and glycerine, but not in ether. Its properties in 

 Antedon hifida and other species of the genus have 

 been described by Moseley (1), Krukenberg (2), and 

 MacMunn (3), to whose papers the reader is referred.* 



External Characters. 



Antedon is composed of a central disc and five pairs 

 of long and flexible arms fringed with pinnules (PI. I., 

 fig. 2). The disc consists of a shallow cup or calyx, 

 composed of a number of calcareous plates firmly articu- 

 lated together, and a lenticular visceral mass, lodged 

 within the cavity of the calyx, and containing the central 

 parts of the ambulacral, nervous, and vascular systems in 

 addition to the alimentary canal. A number of jointed 

 appendages called cirri, each terminating in a claw, are 

 attached to the sloping sides of the central plate of the 

 calyx (PI. I., fig. 3, ci.). The opposite face of the disc is 

 the " tegmen calycis " (PI. II., fig. 24, tg. cl.). Near its 

 centre is the mouth (mth.), surrounded by five slightly 

 elevated valvular folds (PI. II., fig. 28, v.f.). The tegmen 

 calycis is traversed by five ambulacral grooves, fringed 

 with delicate tentacles (PI. II., fig. 24, cnnh. gr.), which 

 radiate from the mouth to the edge of the disc and there 

 bifurcate to enter and traverse the entire length of the 

 ten arms and all their pinnules except the first or 

 proximal one (fig. 24). In one of the five iuterradial 



-'• The black numerals in brackets refer to the list of references 

 given at the end (p. 40), 



