PLATE IV. 



Fig. 1. Orbicella annularis Dana, a small head, natural size. 



Fig. 2. Orbicella annularis Dana, a group of calicles, magnified, showing the process of nuiltiplication by 



gemmation (small calicle in the middle), and by division in the large double calicle below. 

 Fig. 3. Orbicella annularis Dana, a calicle, more magnified. 

 Figs. 4, 6. Orbicella annularis Dana, calicles, in profile, magnified. 

 Fig. 5. Orbicella annularis Dana, calicles from above, magnified. 

 Fig. 7. Orbicella annularis Dana, group of polyps, contracted, natural size. 

 Fig. 8. Orbicella annularis Dana, part of group figured in fig. 7, magnified ; the mouth-disc and the 



tentacles are concealed by the contraction of the outer sphincter. 

 Fig. 9. Orbicella annularis Dana, a polyp expanded, magnified. 

 Fig. 10. Orbicella annularis Dana, polyp expanded, seen from above. 



