52 



THE INORGANIC CONSTITUENTS OF MARINE INVERTEBRATES. 



From these analj-scs no positive conclusions can be drawn. In No. 1 the older layer is 

 much impoverished in magnesium carbonate, and its porous character indicates an alteration 

 by leaching. In No. 2 the difference is very slight, but the older branches are a little richer in 

 magnesia than the younger ones. That differences of composition may exist in different parts 

 of the same specimen is, however, manifested. 



To Prof. L. R. Gary, of Princeton University, we are indebted for two unpublished analyses 

 of calcareous algae by Prof. A. H. Phillips. In one, from Samoa, he found 36.36 per cent of 

 magnesium carbonate, an astonishingly high figure. In the other, from southern Florida 

 or the Tortugas he found, in percentages, CaCOg, 73.23; MgCOj, 25.32; and CsL^Pfig, 0.35; 

 total, 98.90. This analysis agrees well with ours of Goniolithon from the same region. 



Of the earlier analyses of calcareous alga; those by A. Damour *' are the most complete 

 and most nearly comparable with ours. Five species were analyzed, as follows: 



1. Lithdjihi/Uurn sp. Mediterranean Sea. 



2. Mtiohcsiii s]>. Coast of Algeria. 



3. Amphiroa Irihulus. Antilles. 



4. Halimeda opunlia. Red Sea. 



5. Galaxaurafragilis. Antilles. 



Damour's " MiUepora cervicornis," of which he gives an analysis, is not included here on 

 account of its doubtful character. (See p. 15.) 



Damour's analyses of algse. 



In these analyses NajO, K,0, CI, and SO, evidently represent sea salts. Rejecting them 

 as impurities, together with the organic matter, water, and sand, and recalculating to 100 per 

 cent, we have the following reduced analyses, which are similar to ours: 



Damour's analyses reduced. 



■ Damour, A., Compt. Rend., vol. 32, p. 253, 1S.51. 



