244 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



sample was taken. The following work has been done on them: (i) 

 mechanical analyses were made at the U. S. Bureau of Soils, under the direc- 

 tion of Dr. F. K. Cameron, formerly chemist of that Bureau; (2) chemical 

 analyses were made of the samples and of certain important foraminifera by 

 W. C.Wheeler and Alfred A. Chambers in the U. S. Geological Survey Chemical 

 Laboratory; (3) Dr. Albert Mann, of the U. S. Bureau of Plant Industry, has 

 furnished a list of the diatoms; (4) Dr. Marshall A. Howe, of the New York 

 Botanical Garden, has prepared a report on the calcareous algae; (5) Dr. 

 J. A. Cushman, of the U. S. Geological Survey, has written a report on the 

 foraminifera; (6) Dr. Marcus I. Goldman, of the U. S. Geological Survey, 

 undertook to determine for two specimens the percentage of ingredients 

 according to origin. 



SOURCES OF THE MATERIAL. 



Chemically precipitated material. — Inspection of the mechanical analyses 

 on page 246 shows that on line I the maximum content of silt and clay is 

 600 feet from shore, where it is 2.8 per cent; while the minimum is at 1,200 

 feet from shore, where it is only 0.9 per cent. The analyses indicate the 

 presence of very little bacterially or inorganically precipitated calcium car- 

 bonate, as such material originally, at least, is very finely divided. Should 

 such precipitation have taken place, nearly all the material has been removed. 



Coccolithophoridce. — Some of these organisms are found in the sediments 

 of silt size, and coccoliths occur in that of clay size, but in these samples they 

 are of decidedly subordinate importance as contributors of material. 



Diatoms. — These are present, but in an unimportant amount. An 

 account of them by Dr. Mann may be found on page 297 of this volume. 



Coralline algce. — -These organisms are of great importance and are spe- 

 cially described by Dr. Howe. (See pages 291-296 of this volume.) Besides 

 forming what Dr. Mayer designates the "Lithothamnion ridge," they incrust 

 nearly all the dead coral and are important contributors of MgC0 3 . 



Foraminifera. — -This, another highly important group, is reported on in 

 detail by Dr. Cushman, pages 289-290 of this volume. Polytrema mineaceum 

 (plate 97, figures 1, la) incrusts much of the dead coral, as it does in nearly 

 every place where reef-corals are found. 



Madreporaria. — Dr. Mayer has discussed the abundance of this group, 

 and I have described the fauna in the paper which precedes this one. 



Alcyonaria. — This group is given a caption, as it is important in the 

 Bahamas and Florida. Spicules occur in nearly every, if not every, shoal- 

 water sample which I have examined from those areas, but there are few or 

 none in the Murray Island specimens. The abundance of such spicules in 

 samples from the former area, and their scarcity or absence in samples from 

 the latter, constitute the most striking difference between reef samples from 

 the two areas. However, in other Australian reef areas they are probably 

 important, as Alcyonaria are abundant in many places, and especially in 



