124 



ZOOPHYTES. 



moreover, the material has a higher degree of hardness, that of Arragonite being desig- 

 nated by 3j to 4, while common calc spar or rhombohedral carbonate of lime is 3. 

 These remarks, it will be perceived, bear upon the internal calcareous secretions of other 

 animals. In connexion, it should be observed, however, that distinct rhombohedrons of 

 calc spar have been detected by Carpenter in the shells of some molluscs. 



With regard to the structure of the horny axis of the Gorgonire, we have nothing 

 to add to what is stated in the text. In structure, growth, and vitality, they appear 

 to correspond to the horny secretions of other animals. 



Much yet remains to be done in investigating the microscopic structure of corals, and 

 we may express the hope that one who has been so successful in his examinations of 

 molluscs, may extend his researches to this department of science. 



Composition of Corolla. — p. 56. 



It has been stated that the chemical analyses of corals were undertaken for this work 

 by Mr. B. Silliman, jr. The following pages contain the results of his researches, which 

 will be found to be highly important, both in a physiological and geological point of view. 



" No extended researches on the chemical constitution of corals have been made, it is 

 believed, since Mr. Hatchett's, already quoted in this work. This chemist did not operate 

 quanlitively on any of the species examined by him ; and his investigation tended to show 

 that the calcareous corals, as well as the coverings of most of the molluscs, experimented 

 upon, consisted merely of carbonate of lime. Such was the opinion with which these 

 chemical examinations were commenced. But while it has been found that carbonate of 

 lime is the principal ingredient, other elements have been detected, showing that coral is 

 far from being the simple calcareous material supposed. 



"The following is a list of the species examined, which are here numbered for the con- 

 venience of reference : 



1. Porites favosa, Sandwich Islands. 10. 



2. Porites nigrescens, Feejees. 17. 



3. Porites limosa, Feejees. 18. 



4. Porites cylindrica, Feejees. 19. 



5. Porites fragosa, Feejees. 20. 



6. Porites,* Paumotu. 21. 



7. Porites,* Wakes Island. 22. 



8. Porites,* Wakes Island. 23. 



9. Madrepora pnlmata, West Indies. 24. 



10. Mad. spicifera, Ceylon. 25. 



11. Mad. prolifera, Bermuda. 20. 



12. Mad. plantaginea, Ceylon. 27. 



13. Mad. cytherca, Tahiti. 28. 



14. Madrepora, Feejees. 29. 



15. Madrepora, Feejees. 30. 



Madrepora, Feejees. 



Madrepora, Feejees. 



Mad. cyclopea, Wakes Island. 



Pocillopora damicornis, Sooloo. 



P. elonirata, Ceylon. 



P. grandis, Feejees. 



P. ligulata, Sandwich Islands. 



P. cespitosa, Sandwich Islands. 



Millepora tortuosa, Feejees. 



Heliopora crerulca, East Indies. 



Gemmipora brassica, Feejees. 



Dendrophyllia nigrescens, Feejees. 



Mcandrina phrygia, Ceylon. 



Astraa orion, Ceylon. 



Astraja (pi. 13, fig. 15). 



* Worn specimens, not identified. 



