22 Thomas G. Thompson and Tsaihwa J. Chow 



weighed samples (0-5 to 1 -0 gram) of the dried materials were heated in an oven to a temperature of 

 350° C and then cooled. The loss in weight was designated as the organic matter. The samples were 

 then further ignited at 1,100° C until all carbonates were decomposed. Upon cooling and weighing, 

 the difference in weight was considered as carbon dioxide. The residues were treated with 10 ml of 

 water, and 12 N hydrochloric acid was added dropwise until solution was complete. The solutions 

 were then diluted to one litre, thoroughly mixed, and analyzed for strontium and calcium using the 

 "internal standards" technique of flame photometry by Chow and Thompson (1955 a and b). 



RESULTS OF ANALYSIS 



All analyses were made on the fresh calcareous skeletons (unless otherwise stated) which had been 

 carefully cleaned and air-dried for several weeks. In order to obtain a general idea of the distribution 

 of strontium in the biosphere, a large variety of species of carbonate-secreting marine organisms was 

 analyzed, rather than concentrating on possible variations in just a few particular species. 



In tables the calcium, strontium, carbon dioxide and organic matter content of the organisms are 

 reported as percent of constituents in air-dried samples. To demonstrate more clearly the relation of 

 the strontium to the calcium, it was deemed desirable to report this relationship as the atom ratio 

 of strontium to calcium. For example, the calcareous alga, Bossea orbigniana, contains 01 99% of 

 strontium and 29-2% of calcium. The strontium-calcium atom ratio would be: 



0-199/87-63 



= 312 X 10-3 



29 -2/40 08 



and indicates that for every 1 ,000 atoms of calcium there are present approximately three atoms of 

 strontium. 



The mineralogical data cited in this paper were taken from the publications of Boggild (1930), 

 Vinogradov (1953) and Chave (1954). However, the mineralogical properties of the specimens, 

 which were analyzed chemically by the authors, will be studied further by Dr. R. G. Bader. 



DISCUSSION 



Phylogenetic Aspects: 



1. Marine Algae: In most of the previous studies on calcareous algae, determina- 

 tions of calcium and magnesium were given, the calcium carbonate in the skeletons 

 being reported as calcite. Only one analysis of strontium was reported, which showed 

 0-26% of strontium in the ash of Lithothamnion polymorphum (Noll, 1934). 



The results of analysis of calcareous algae, Corallinaceae, are shown in Table 1(A). 

 The average strontium-calcium atom ratio was 3-20 x 10-'. The diatoms, Coscino- 

 discus, were also analyzed. As they are primarily of a silicious nature, only traces of 

 calcium were found in the skeletons. 



2. Phylum Protozoa: The calcium content of Foraminifera has been investigated 

 extensively, especially its relation to the origin of calcareous marine sediments, but 

 no strontium determinations appeared in the literature. 



Analyses of calcareous Foraminifera (Table I (B)) by the authors showed an average 

 strontium-calcium atom ratio of 3-07 x 10-'. The presence of magnesium in the 

 skeletons was detected qualitatively. It has long been known that radiolarian skeletons 

 are rich in strontium, but the authors were unable to collect sufficient material for a 

 quantitative study. 



3. Phylum Porifera: The classification of sponges is based on the chemical com- 

 position of the skeletons such as the Calcarea containing calcite spicules. Fox and 

 Ramage (1931) noted the presence of strontium in Porifera when they examined the 

 ash of Clathrina spectroscopically. 



