PLATE XXVIII. 



Alcyonaria. 



Figure 1. Isis Dan^, Duncan. A large joint, natural size. 



2. End of a joint, showing the radii, magnified. 



3. A variety. The joints with lateral projections, natural size. 



4. Isis compressa, Duncan. The stem, natural size. 



5. The top of a joint, magnified. 



6. Isis elongata, Duncan. Portions of the stem and joints, natural size. 



7. A transverse section, slightly magnified. 



8. Isis, species 1. A joint, side view, natural size. 



9. The upper surface, slightly magnified. 



10. Joints of another Isis, natural size. 



11. Isis, species 2. A joint, natural size. 



12. Isis, species 3. Two joints, natural size. 



13. The striation, magnified. 



14. The convex upper surface, magnified. 



