50 



THE INORGANIC CONSTITUENTS OF M.\RINE INVEP,TEBR.\TES. 



In No. 12, Amphiroa, the hi<jli silica and sesquioxidcs are evidently impurities. If they 

 are rejected, the percentage of magnesium carbonate rises to 18.41. 

 Of Halimeda, four species were analyzed, as follows: 



17. Haliiiieda opuntia Lamouroux. Key West, Fla. 



18. Ilulimeda simulatis Howe. East of Guanica Harbor, Porto Rico. 



19. Ilnliineda Iridens La,mouronx. Cayo Maria Langa, Bay of Giiayanilla, Porto Rico. 



20. UaUmeda monile Lamouroiix. Same locality as No. 19. 



Analyses of nalimeda. 



SiO., 



(Al.Fe)A 



MgO 



CaO 



PA 



SO3 



Ignition 



C02 needed 



Organic matter, etc 



17 



0.37 



.20 



.01 



50. 32 



Trace. 



.07 



48.20 



99.17 



39.47 



8.73 



18 



0.44 



.18 



.19 



50. 20 



Trace. 



.23 



48.38 



99.62 



38. .53 



8.85 



Reduced analyses of Halinuda. 



After allowance is made for obvious impurities the essential identity of these four analyses 

 becomes clear. The inorganic portion of Halimeda. consists of calcium carbonate and an insig- 

 nificant amount of magnesia. In the first group of algae, Nos. 1 to 16, magnesium carbonate 

 is conspicuous, more so than in any other class of organisms so far analyzed. In Goniolithon 

 strictum especially it ranges from 24 to over 25 per cent, or more than haKway to dolomite. 

 These algae are probably the largest contributors of magnesia to the marine limestones. 



It is also noteworthy that the two algse of the first group, Nos. 1 and 13, are from the cold 

 waters of Newfoundland, and that the others are from tropical or subtropical regions. Several, 

 if not all of them, are shoal-water organisms and were collected on reefs, or rocks, or on sands 

 near low-tide levels. It is desirable that Arctic species should be carefully studied — at least 

 more carefully than hitherto. The older published data leave much to be desired, especially 

 as to definiteness of species and localities. 



In addition to the material received from Dr. Howe, three more calcareous algie were 

 submitted for analysis by T. Wayland Vaughan. The species, with analyses by A. A. Chambers, 

 are as foUows: 



1. Goniolithon fratescens Foslie. Cocos-Keeling Islands, in the Indian Ocean; latitude, 12.5° S.; longitude, 

 96.53° E. 



2. Goniolithon orthoblaslum (Heydrich) Howe. Murray Island, Torres Straits, Australia. 



3. Lithophyllum kaiseri Heydrich. Cocos-Keeling Islands. 



