56 BULLETIN" OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 



Fig. 5. Enlarged view of the interbrachial region of a young starfish. The 

 odontophore, H>, appears as a heart-shaped plate in the angle of the raj. Actinal 

 view. Same age as' Plate II. Fig. 1. 



Fig. 6. The same, somewhat older. Actinal view. 



Fig. 7. Still older view of the same. 



Fig. 8. View of an older stage, in which a second interbrachial, iV 1 , has formed. 



The shaded plates of Figs. 5, 6, 7, and 8 are oral ambulacrals and ambulacral 

 rafters. The two crescentic plates, unshaded, in the upper part of Fig. 5, are 

 the edges of the terminals, not marginals, m, of Figs. 6, 7, and 8. 



