2S8 



PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



tory of the Carnegie Institution of Washington, are "hexagonal plates set 

 edgewise. They are optically positive, co = about 1.535, € = about 1.560. These 

 are surely not aragonite, but I can find in the mineral tables nothing cor- 

 responding to them."^ They require further study. 



Summaries, sample No. sj^^j. 



Silt:\{sample No. 27337). — Contains coccolithophoridae {Pontosphara), 

 minute foraminifera, sponge spicules, etc. 



Clay {sample No. 27337). — In this clay round coccoliths are abundant; 

 "there are numerous calcite grains and rhombs which appear exactly like 



'Letter of May 9, 1916, from Dr. H. E. Merwin. 



'See discussion following. 



