SUBMARINE DEPOSITS. 281 



over eighty per cent. The variation in the percentage of lime 

 in pteropod ooze is from sixty-eight to eighty-three. In the 

 coral muds and pteropod and globigerina ooze, the Hme is re- 

 placed in part, in accordance with the locality, by a greater or 

 smaller amount of siliceous organisms or by argillaceous matter. 

 The variations of Hme in globigerina ooze range from thirty-two 

 to seventy-two j)er cent, in proj)ortion to the proximity of the 

 shore, the percentage of mineral residue varying from sixty-four 

 to twenty-seven, in addition to the changes due to a larger or 

 smaller proportion of siliceons organisms or argillaceous matter. 



While sounding, it was easy to follow the depth and the dis- 

 tance from shore by the gradual decrease of bright tints in the 

 bottom specimens ; these were probably colored more intensely 

 by organic matter when close in shore, but became bleached 

 with increasing depth. Along the lines of soundings in the 

 Caribbean, we found the coral muds to be of a light greenish- 

 gray or yellowish tint. Pteropod ooze varied from a chalky 

 gray to white, while globigerina ooze passed from dark brown 

 to reddish, reddish brown, and light brown, or cream-color. 

 The river muds were usually gray or brown. 



The globigerina and pteropod ooze of the central parts of the 

 basins of the Gulf of Mexico and the Caribbean, like those 

 found in proximity to the Greater and Lesser Antilles, differ ma- 

 terially from similar deposits in the great oceanic basins. The 

 siliceous organisms consist of radiolarians and sponge spicules, 

 with a few diatoms ; but these seldom make up more than three 

 or four per cent of the whole deposit. An unusual number of 

 otoHths of fishes were detected in the bottom specimens of the 

 Gulf of Mexico ; they occurred at considerable depths, from 392 

 to 1,568 fathoms. Fish teeth were also found in some of the 

 mud deposits, from over 500 fathoms. 



I take the following from Murray's Report : — 



" The phosphatic concretions in the dredgings in the Straits of Flo- 

 rida are very interesting. In a great many deep-sea deposits there is 

 usually a small percentage of phosphate of Hme, but near the shore, 

 in some instances, the quantity is very considerable. Sharpies, who 

 analyzed the ooze of the Gulf Stream, found over eighty-five per cent 

 of carbonate of Hme, and only 0.18 per cent of phosphate of lime. 



