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PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



(4) The minor chemical constituents of the bottom samples and rocks 

 are as follows: Si0 2 , which ranges from 0.07 to 0.29 per cent, an amount so 

 small as mostly to be accounted for by sponge spicules and the few diatoms; 

 (Al, Fe) 2 3 ranges from 0.08 per cent to o. 1 5 per cent. It is evident that in the 

 Bahamas no appreciable amount of earthy material has been derived from 

 land areas. The small amount of Fe 2 3 , about 0.12 per cent, is sufficient 

 to produce iron stains and red earth when secondarily concentrated. One 

 oolite sample shows a trace of Ca 3 P 2 8 , but none was found in the bottom 

 samples examined for it. CaS0 4 ranges from a trace to 0.24 per cent. 

 The presence of a small amount of CaS0 4 seems necessary for the produc- 

 tion of aragonite at ordinary temperatures; 1 and as the oolitic muds and 

 oolites are largely aragonite, the importance of CaS0 4 is evident. 



BOTTOM SAMPLES FROM FLORIDA. 



Five bottom samples and two oolite specimens are specially considered. 

 In a previous publication 2 I have discussed in a preliminary way the marine 

 bottom deposits forming in the bays and sounds behind the Florida Keys 

 and Mr. G. C. Matson contributed to the same paper a report on his 

 examination of a set of samples. A smaller number of samples will here 

 be described in more detail than those dealt with in the paper cited. 



Specimen No. 68 is a beach sand from the east side of Sands Key, which is near the north 

 end of the line of the Florida keys. (See plate 95.) 



Specimen Nos. 91, 97, and 98 are examples of lagoon deposits. No. 91 is from a mud flat 

 north of Loggerhead Key, south of Cudjoe Key and east of Sugarloaf Key; water 

 3 or 4 feet deep. No. 97 is from near the obstruction buoy, off the northwest 

 entrance to Fort Jefferson channel, Tortugas; depth about 7 fathoms (specimen 

 collected by Dr. A. G. Mayer). No. 98 is from the east side of Marquesas lagoon; 

 water about I foot deep. (For position of the stations according to number, see 

 plate 95.) 



Specimen No. 100 was taken by Mr. John B. Henderson in water 60 fathoms deep, south of 

 Sand Key light, off Key West. (See plate 95.) 



The oolite samples are from Miami and Boca Grande Key. 



The following are the results of mechanical analyses (by the U. S. Bureau 

 of Soils) of samples of sea-bottom specimens from Florida: 



Mechanical analyses of sea-bottom samples from Florida. 



[For graphic illustration, see plate 94.] 



'Johnston, Merwin, and Williamson, Am. Jour. Sci., vol. 41, p. 509, June 1916. 

 2 Carnegie Inst. Wash. Pub. 133, pp. 114-125, 1910. 



