CHARACTERISTIC DEEP-SEA TYPES. RHIZOPODS. 159 



rliizopods flourish, between 150 and 400 fathoms, consists 

 mainly of a chalky, tough, amorphous ooze, — a modified pter- 

 opod and globigerina ooze. Mixed with this are grains of sim- 

 ilar material, but of a greater consistency, together with dead 

 shells of pelagic mollusks and foraminifers and a great number 

 of the tests of dead rhizopods, which once lived on the bottom 

 and among which flourished in great abundance the innumer- 

 able large and small species characteristic of the Caribbean dis- 

 trict. The majority of the largest rhizopods occur on the 

 bottom, which is covered with the coarser fragments of coral- 

 lines, annelid tubes, and other pieces of limestone, soldered to- 

 gether more or less compactly, and transformed into rough 

 masses and lumps resembling coarse mortar or gravel. 



Associated with the arenaceous, siliceous, and calcareous rhizo- 

 pods which undoubtedly live upon the bottom, we find the tests 

 of Globigerinse, Hastigerinae, Pulvinulinae, and many others 

 which have also been observed as pelagic. For a time it was 

 supposed that the deposits so widely extended were due to Glo- 

 bigerinse living on the bottom, but the evidence gradually 

 brought forward by Bailey, Johannes Mliller, Pourtales, Major 

 Owen, and especially by Mr. Murray of the "Challenger," seems 

 to leave no doubt that the Foraminif era to which the globigerina 

 ooze is due are pelagic, the ooze being formed by the dead shells 

 after they have reached the bottom. 



One of the most common types of rhizopods is B'lJoculina 

 rmgens (Figs. 484, 484 a, 484 6), a most abundant form in 



Fig. 484 a. \. Fig. 484 b. \^. 



Biloculina ringens. (Goes.) 



deep water in the Atlantic ; it is found nearly everywhere, from 

 the littoral region to a dejjth of 3,000 fathoms. Along our 

 coast off Block Island, and in a portion of the area between 



