352 



Biology in Americo. 



feet greater than the height of Everest, which is the greatest 

 depth yet recorded in any ocean. This deptli was found by 

 tlie U. !S. 8. "Nero," in the north raeiiic near the island of 

 Guam. 



The floor of the ocean is covered with fine ooze composed 

 largely of the fragments of shells of many kinds of animals 

 and some plants, predominant among which in many places 



A Eadiolarian 

 Courtesy of the American Museum of Natural History. 



are the minute and wonderfully sculptured shells of uni- 

 cellular animals, Radiolaria, and Foraminifera, which in life 

 are floating at the surface of the sea. The shells of these 

 minute creatures often make up so large a part of the bottom 

 deposits, that the latter are named from them. One of the 

 commonest of them is Globigerina, which has given its name 

 to extensive bottom deposits in the sea. The shells of 

 certain small species of molluscs, the pteropods or "wing- 



