TWO GIGANTIC TYPES OP ARENACEOUS EORAMINIEERA. 
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shows the internal surface of a lamella separated by concentric fracture, the conical radial 
processes remaining attached to it, as represented on a larger scale in Plate LXXIV. 
fig. 3 : — b shows the appearances presented by a similar fracture which has passed through 
the radial processes, so as to lay open their cancellated structure, as represented on a 
larger scale in Plate LXXIY. fig. 1 : — c shows the result of a tangential section passing 
through the cancellated substance of a lamella, as represented on a larger scale in Plate 
LXXIY. fig. 4 : — d shows the appearances presented by the external surface of a lamella 
separated by a concentric fracture which has passed through the radial processes, as 
represented on a larger scale in Plate LXXIV. fig. 2 ; — and e shows the aspect of sections 
taken in a radial direction, so as to cross the solid lamellae and their intervening spaces, 
as represented on a larger scale in Plate LXXIII. figs. 3, 4. — Magnified 7 diameters. 
PLATE LXXIII. 
Fig. 1. Portion of section which has cut the central chambered cone transversely: — 
s, one of its sinuous partitions; l, l, the first layer of labyrinthic structure, 
built up on its external wall, around which are seen successive layers of the 
like structure, separated by interspaces which are traversed by the radial 
tubes, t , t, t, t, one of which is seen laid open at t. Towards the right-hand 
side of the figure, the progressive increase in the amount of labyrinthic struc- 
ture in each concentric layer is apparent. — Magnified 25 diameters. 
Fig. 2. Portion of section which has cut the chambered cone longitudinally : — c\ c 2 , e 3 , 
c\ c 5 , its successive chambers separated by sinuous partitions ; d, its termi- 
nation, with the commencement of the labyrinthic structure shown at l . — 
Magnified 25 diameters. 
Figs. 3, 4. Portions of sections traversing the concentric layers in a radial direction, so 
as to show the manner in which the cancellated structure of each lamella is 
built up on a solid layer or floor, which cuts it off from the interspace, int , 
beneath it. In fig. 3 the manner in which the interspaces are bounded late- 
rally by the radial processes connecting the successive layers is well seen ; 
and in fig. 4 two of the radial tubes, t, t, contained in those processes are shown 
laid open, so as to exhibit their connexion with the labyrinthic structure. — 
Magnified 25 diameters. The free communication of the labyrinthic structure 
on its outer or peripherad aspect, with the interspace separating each lamella 
from that which succeeds it, is well seen in both figures ; the lower margin of 
which looks towards the centre of the sphere, and the upper to its periphery. 
PLATE LXXIV. 
Fig. 1. Portion of the internal surface of a lamella, separated from that whereon it was 
deposited, by a concentric fracture which has passed through the radial pro- 
cesses rp,rp , in each of which are seen one or more large orifices of the radial 
mdccclxix. 5 p 
