CHARACTERISTIC DEEP-SEA TYPES. — RHIZOPODS. 167 
Orbulina universa, a cosmopolitan species, dates back to the 
lias and is very common in the tertiary. It is widely distributed 
on the coralline and ooze of the Caribbean, and one of the 
pelagic types most frequently found. Pourtalés discovered that 
bottom specimens of O. universa did not always consist of a 
simple chamber, but generally included three or four chambers 
(Fig. 510), resembling young Globigerine more or less devel- 
oped, and attached to the inside by slender spicules. Krohn 
observed the same in living specimens. It seems probable that 
the Globigerine in the chamber are resórbed, and that the vis- 
ible spherieal chamber is the last segment, considered at one 
time to be a special reproductive chamber, and capable of wide- 
spread existence. The Globigerine are eminently pelagic, some 
of the genera exclusively so, and the shells when alive are thin 
and transparent. 
The shell of Globigerina is composed of a series of hyaline 
and perforated chambers of a spheroidal form, arranged in a 
spiral manner, with the apertures of each chamber opening 
round the umbilicus. The young shells are made up of fewer 
and comparatively larger chambers. The tests of Globigerina 
Fig. 511. Fig. 511 a. Fig. 511 b. 
Globigerina bulloides. 15. (Gods. ) 
bulloides (Figs. 511, 511 a, 511 0) and of Orbulina universa 
(Fig. 512) are among the most common deep-water rhizopods. 
Globigerine are spinous in their early stages, and probably more 
or less so when the shell has attained its full 
development, but the spines are of such extreme 
tenuity that, when taken with the tow-net, they 
are invariably broken. Bottom specimens have 
no spines, and these may be present perhaps only _ 
in the pelagic stage; the delicate calcareous e nie 
spines, from four to five times the diameter of the — 9. (Goös.) 
