62 BULLETIN OF THE 



than 2,000 fathoms the Pteropod and Heteropod shells appear to be 

 nearly, if not quite, absent, — the carbonate of lime then consisting of 

 the shells of pelagic Foraminifera ; in less depths the Pteropod and 

 Heteropod shells are present, and in depths varying from 200 to 500 

 fathoms they make up the bulk of the deposits in many places. In 

 several of the deposits, where the percentage of carbonate of lime is very 

 high, the whole has a very chalk-like appearanee ; it appears, indeed, as 

 if it were in the process of transformation to true chalk. 



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. 



Phosphatic Concretions. — The phosphatic concretions in the dredg- 

 ings in Florida Strait are very interesting. In a great many deep-sea 

 deposits there is usually a small percentage of phosphate of lime, but 

 near the shore, in some instances, the quantity is very considerable. 

 Sharpies, who analysed the ooze of the Gulf Stream, found — 



Carbonate of Lime 85.62 



" of Magnesium 4.26 



Silica 1.32 



Alumina 



Oxide of iron 0.31 



PuospHATE OF Lime 0.18 



Loss on ignition 8.15 



100.04 



In certain concretions found by the " Blake " in the Florida Strait, 

 and by the " Challenger " in various parts of the world near land, the 

 quantity of phosphate of lime is very much greater than in the deposits. 

 These concretions appear always to be associated in an intimate way 

 with organisms. 



In 125 fathoms S. W. of Land Key, Florida, a fragment of bone was 

 obtained several centimetres in diameter. It was of a dirty brown 

 color, of great hardness, and had a conchoidal fracture. A microscopic 

 examination of thin sections showed that the bone structure was per- 

 fectly preserved. 



The following is the result of an analysis of this specimen by M. 

 Klement : — 



Phosphoric acid (PjO^) 33.42 



Carbonic " (COj) ...... 5.80 



