124 ZOOPHY TES. 
moreover, the material has a higher degree of hardness, that of Arragonite being desig- 
nated by 32 to 4, while common cale 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 
cale spar have been detected by Carpenter in the shells of some molluscs. 
With regard to the structure of the horny axis of the Gorgoniw, 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 Coralla.—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 haye been made, it is 
believed, since Mr, Hatchett’s, already quoted in this work. This chemist did not operate 
quantitively 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 fayosa, Sandwich Islands. 16. Madrepora, Feejees, 
2. Porites nigrescens, Feejees, 17. Madrepora, Feejees. 
3. Porites limosa, Feejees. 18. Mad. cyclopea, Wakes Island. 
4. Porites cylindrica, Feejees. 19. Pocillopora damicornis, Sooloo. 
5. Porites fragosa, Feejees, 20. P. elongata, Ceylon. 
6. Porites,* Paumotu. 21. P. grandis, Feejees. 
7. Porites,* Wakes Island. 22. P. ligulata, Sandwich Islands. 
8. Porites,* Wakes Island. 23. P. cespitosa, Sandwich Islands, 
9. Madrepora palmata, West Indies. 24. Millepora tortuosa, Feejees. 
10. Mad. spicifera, Ceylon. 25, Heliopora cerulea, East Indies, 
11. Mad. prolifera, Bermuda. 26. Gemmipora brassica, Feejces. 
12. Mad. plantaginea, Ceylon. 27. Dendrophyllia nigrescens, Feejees. 
13. Mad. cytherea, Tahiti. 28. Meandrina phrygia, Ceylon. 
14, Madrepora, Feejees. 29. Astraea orion, Ceylon. 
15. Madrepora, Feejees. 30, Astrea (pl. 13, fig. 15). 
* Worn specimens, not identified. 
