EXPLANATION OF THE PLATES. 



To avoid useless repetitions in the description of the Figures, the 

 parts. It will greatly facilitate the reading of this memi 



me letters are used, throughout these Plates, to denote identical 

 r to become familiar with the notation here adopted. 



EXPLANATION OF THE LETTERING 

 ON PLATES L — VIII. 



a, anus. 



b, dorsal or water pore, madreporic opening. 



c, alimentary canal. 



d, digestive cavity, stomach. 



d', abactinal water-tubes in angle of rays of young Star- 

 fish, 

 rf", water-tubes of lateral line of rays of young Starfish. 

 d"', water-tubes of median line of rays of young Starfish. 



e, eye of Starfish at base of odd tentacle (£'). 

 e 1 , median anal arms of Brachiolaria. 



e", dorsal anal arms of Brachiolaria. 

 e'", ventral anal arms of Brachiolaria. 

 e"", dorsal oral arms of Brachiolaria. 

 e 6 , ventral oral arms of Brachiolaria. 

 e°, odd terminal oral arm of Brachiolaria. 



f, brachiolar arms. 



/', branch of water-tube {vow 1 ) leading into /. 

 /", odd brachiolar arms. 



/'", surface-warts at base of odd brachiolar arm (/"). 

 h, hole of cul de sac of water-tube w. 

 I, central abactinal plate of young Starfish. 

 h, h, h, ■ ■ interbrachial abactinal plates of young Star- 

 fish. 

 h, fe, fe ■ • brachial plates of young Starfish. 

 m, mouth. 



m', pistol-shaped oral pouch of oesophagus, 

 m", anal pouch of oesophagus. 

 n, opening for passage of ambulacral sucker. 



o, oesophagus. 



p, spines on edge of ray of Starfish. 



Pi, spines of exterior rows along abactinal surface of rays. 



Pi, spines of middle row on abactinal surface of rays. 



Pz, central spine of abactinal surface of Starfish, on cen- 

 tral plate (7i). 



P , plate at junction of adjacent rays (ovarian plate). 



p', p 1 ', different forms of pedicellarise. 



r, abactinal surface. 



r', first set of five limestone rods which appear on abac- 

 tinal surface, and which eventually become the brachial 

 plates (7 2 ). 



r", second set of five interbrachial limestone rods, which 

 eventually become the interbrachial plates (7i). 



r"-r 5 ", rays of young Starfish; r-[ being ray next to 

 madreporic body, when Brachiolaria is seen from the 

 dorsal side. 



st and s, actinal region. 



t, t, t, . . tentacles of the young Starfish. 



t 1 , odd tentacle. 



;", ambulacral tube. 



!(, lateral ambulacral plates, surmounted by spine. 



u', median ambulacral plates with very small spines. 



v, vibratile chord, anal part. 



v 1 , vibratile chord, oral part. 



w, water-tube, developing abactinal area. 



id', water-tube of Brachiolaria leading to madreporic open- 

 ing (b), developing actinal area. 



ww 1 , portion of water-tube of Brachiolaria formed by 

 iunction of w and w 1 . 



(1) 



