54 



THE INORGANIC CONSTITUENTS OF MARINE INVERTEBRATES. 



In this series the percentages of magnesium carbonate are much lower than those found by 

 us, and there is uncertainty in six examples as to the exact species. Hogbom, however, points 

 out the importance of these algae in respect to the formation of dolomite, which was the real 

 subject of his investigation. In Halimeda sp., from Labuan, only a trace of magnesia was found. 



In Lifhothamnivm racemus, from the Bahamas, H. W. Nichols^" found 5.35 per cent of 

 magnesium carbonate, but without rejection of organic matter, etc., undetermined. This 

 percentage is remarkably low. A similar low figure for magnesium carbonate — 5.85 per cent — 

 was found by E. W. Skeats ^" in Lithotharmuum phUlipi var. funafittii'iiKis Foslie. The speci- 

 men was taken on tiie atoll of Funafuti. 



In a very fresh Halimeda opvritia Skeats found 0.60 per cent of MgCOj and 86.50 of CaCOj, 

 hut in a mass of fronds dredged up from a depth between 50 and 60 fathoms the percentages 

 were 4.0 MgCOs to 93.59 CaCOg. The increase in magnesia may have been due to concentra- 

 tion by leaching. These data are given by J. W. Judd," who also cites an analysis of dead 

 Halimeda fronds made for him by C. G. Cullis, who found in them 1.39 per cent of MgCOa and 

 98.32 of CaCOj. Judd also quotes an analysis of Halimeda, cited by Payen in his Flora, which 

 contained 5.50 per cent of MgCOa and 90.16 of CaCOj. The character of the specimen repre- 

 sented by the last analysis, whether fresh or old, is uncertain. The best analyses agree in 

 assigning little magnesium to Halimeda. 



In an important memoir on MeJobesia Madame P. Lcmoine " gives several analyses of 

 calcareous nlgvo. Tlie analyses, made for her by M. C'harf, are not very complete, but they 

 are, nevertheless, of distinct value. The data are as follows: 



1. Lithothamnium ealcareum. St.-Vaast-la-Hongue, Manche, France. 



2. Lithothamnium ealcareum. Isle Glenan, Finistere, France. 



3. Lithothamniwn fornicatum . Norway. 



4. Lithophyllum incrustans. Gatteville, Manche, France. 



5. Lithophyllum incrustans. Mazagan, Morocco. 



6. Lithophyllum tortuosum. Genoa. 



7. Lithophyllum craspedium. Tahiti. 



To the analyses as reproduced in the following table we venture to add a line for reduced 

 or corrected magnesium carbonate, computed on the basis of 100 per cent for the two carbon- 

 ates alone. 



Lemoine^s analyses of algk. 



In this series the highest magnesia is in the alga from Tahiti and the lowest in that from 

 Noi-way. This tendency toward increased magnesia in alg;B from warm regions, as compared 

 with those from cold waters, was noticed by Machimo Lemoine but onlj' incidentally. The 

 subject was not given any detailed consideration by her. 



Madame Lemoine also cites the older analyses of algte, including three by J. Chalon, as 

 follows : 



1. Lithothamnium ealcareum. Roscoff, Finistere, France. 



2. Lithophyllum incrustans. Banyuls, France, on the Mediterranean. 



3. Lithophyllum tortuosum.. Naples. 



" Nichols, H. W., Field Columbian Mus. Pub. Ul, p. 31, 1906. 



» Skeats, E. W., The atoll of Funafuti, pp. 376, 377, London, The Royal Society, 1904. 



51 Judd, J. W., idem. 



'^Lemoine, P., Inst, oc^anographique Monaco Annales, vol. 2, fasc. 2, 1911. 



