CHARACTERISTIC DEEP-SEA TYPES. RHIZOPODS. 159 
rhizopods 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- 
Mar 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 Globigerine, Hastigerine, Pulvinuline, and many others 
which have also been observed as pelagic. Fora time it was 
supposed that the deposits so widely extended were due to Glo- 
bigerine living on the bottom, but the evidence gradually 
brought forward by Bailey, Johannes Müller, Pourtalòs, Major 
Owen, and especially by Mr. Murray of the “ Challenger," seems 
to leave no doubt that the Foraminifera 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 Biloculina 
ringens (Figs. 484, 484 a, 484 b), a most abundant form in 
Fig. 484 a. $. Fig. 484 b. 49. 
1 
Biloculina ringens. (Goös.) 
deep water in the Atlantic; it is found nearly everywhere, from 
the littoral region to a depth of 3,000 fathoms. Along our 
coast off Block Island, and im a portion of the area between 
