NOTES AND MEMORANDA. 69 
of two different sizes, the larger about four times the area of 
the smaller. The larger pores are the less numerous; they 
are scattered over the surface of the shell without any appear- 
ance of regularity; the smaller pores occupy the spaces 
between the larger. ‘The crests between the pores are much 
less regular in Orbulina than they are in Globigerina ; and 
the spines, which are of great length and extreme tenuity, 
seem rather to arise abruptly from the top of scattered 
papille than to mark the intersections of the crest. This 
origin of the spines from the papille can be well seen with 
a moderate power on the periphery of the sphere. ‘The spines 
are hollow and flexible; they naturally radiate regularly 
from the direction of the centre of the sphere; but in speci- 
mens which have been placed under the microscope with the 
greatest care they are usually entangled together in twisted 
bundles. They are so fragile that the weight of the shell 
itself, rolling about with the motion of the ship, is usually 
sufficient to break off the whole of the spines and leave the 
papille only projecting from its surface in the course of a few 
minutes. In some examples, either those in process of deve- 
lopment, or a series showing a varietal divergence from the 
ordinary type, the shell is very thin and almost perfectly 
smooth, with neither papille nor spines, nor any visible 
structure, except the two classes of pores, which are con- 
stant. 
The chamber of Orbulina is often almost empty; even in 
the case of examples from the surface, which appears from 
the freshness and transparency of the shell to be living, it is 
never full of sarcode; but it frequently contains a small 
quantity of yellow sarcode stuck against one side, as in the 
last chamber of Globigerina. Sometimes, but by no means 
constantly, within the chamber of Orbulina there is a 
little chain of three or four small chambers singularly 
resembling in form, in proportion, and in sculpture, a 
small Globigerina ; and sometimes, but again by no means 
constantly, spines are developed on the surface of the calca- 
reous walls of these inner chambers, like those on the test of 
Globigerina. The spines radiate from the position of the 
centre of the chambers and abut against the insides of the 
wall of the Orbulina. In a few cases the inner chambers 
have been observed apparently arising within or among the 
sarcode adhering to the wall of the Orbulina. 
Major Owen regards Orbulina as a distinct organism, 
nearly allied to Globigerina, but differing so far from it as to 
justify its separation into a special subgenus. He considers 
the small inner chamber of Orbulina as representing the 
