EXPLANATION OF THE PLATES. 



The abbreviations used on Plates 43 and 44 are as follows : 



as = abactinal system of plates, seen from within. 

 cts = connective tissue strands. 

 go = reproductive organs. 

 I = lantern, seen from above. 

 Ic = lower, or aetinal, half of stomach-intestine. 

 m = mesentery. 

 oe — oesophagus. 

 pff = perignathic girdle. 

 r = rectum. 

 sc = stone-canal. 

 uc = upper, or abactinal, half of stomach-intestine. 



In all abactinal and aetinal views of the entire animal and of the denuded test, and in 

 Pis. 43, 44, aud 56, figs. 1, 2, the anterior ambulacrum is uppermost. 



