PLATE X. 



FIG. 1. A sketch of the inferior part of the fossil represented, Fig. 4. In this sketch is 

 seen the arrangement of the circular and the radiating fibres, by the action of 

 which a vacuum would be, probably, formed or destroyed, and the animal 

 thereby fixed or liberated. 



2. A magnified representation of the same fibres. 



3. A magnified representation of the geniculated fibres on the convex surface. 

 4-. The superior convex surface of the fossil. 



5. An alcyonite resembling a cucumber in its form : and bearing some analogy with 



Champignon de Mer of Count Marsilli. 



6. An alcyonite of a very singular form. 



7. A small alcyonite,. almost hemispherical, with a circular central opening. 



8. A small hemispherical alcyonite, with a stellated central opening, and adherent 



to a flat alcyonite. 



9. A small oblong alcyonite, with a circular opening. 



10. A triquetral alcyonite, beset with minute circular pores. This, and the three 



preceding fossils, are from the canton of Basle, Switzerland. 



11. An alcyonite investing a fossil nerite. 



12. An alcyonite found in the chalk-pits of Wiltshire. 



13. An alcyonite which much resembled the one, Plate XI. Fig. 7, deprived of its 



outer surface by the muriatic acid, and shewing the beautiful ramifications of 

 its fibres, or tubuli. 



14. A pebble, the figures on which are formed by the union of circular markings 



similar to those in Fig. 15. 



15. A pebble frequently met with in gravel-pits; the markings on its surface having 



been the holes through which ramifications of an alcyonite have passed. 



16. A pebble of the same kind with the preceding, longitudinally fractured, and 



thus shewing the alcyonite possessing a situation in its centre. 



