CHARACTERISTIC DEEP-SEA TYPES. KlilZUPODS. 



167 



OrhuUna univei'sa, 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. Pourtales discovered that 

 bottom specimens of O. uriiversa did not always consist of a 

 simple chamber, but generally included three or four chambers 

 (Fig. 510), resembling young Globigeriuije 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 Globigerinse in the chamber are resorbed, and that the vis- 

 ible spherical chamber is the last segment, considered at one 

 time to be a S23ecial reproductive chamber, and capable of wide- 

 spread existence. The Globigerinfe 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, wdth the apertures of each chamber opening- 

 round the umbilicus. The young shells are made up of fewer 

 and comparatively larger chambers. The tests of Glohigerina 



Fig. 511. 



Fig. .111 a. 

 Globigerina bulloides. V- (Goes.) 



Fie-. :>1 1 b. 



hulloides (Figs. 511, 511 a, 511 6) and of Orhulina wilversa 



(Fig. 512) are among the most common deei3-water rhizopods. 



Globigerinse 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 ^'^^„i;l^t„;7er^I" 



spines, from four to five times the diameter of the Y- (f^oe.s.) 



