348 THE MEDALS OF CREATION. Cuap. X. 
Nodosarize are abundant in tertiary deposits. Mr. Walter 
Mantell discovered Foraminifera of this genus in the blue 
clay of Kakaunui, in New Zealand. 
CristeLuaria. Lign. 109, fig. 4.—The shell is in the form 
of a compressed Nautilus; it has a single aperture, which is 
situated at the angle of the keel; the cells are oblique. 
This genus comprises seventy fossil species, which occur — 
in the Lias, Oolite, and Chalk. Living species are abundant — 
in almost every sea. 
Frapeviina. Lign. 111, fig. 4a.—In a young state, this 
shell, like the preceding, releednies that of a Nautilus, and 
the cells are oblique; but in the adult, are of a zigzag 
(chevron) form. It has a single round aperture. Jig. 4a 
shows a young individual, seen in profile; jig. 40 a lateral — 
view, exhibiting the obliquity of the cells. 
Species of Flabellina are often found in cretaceous strata. 
The genus is not known in a recent state. Pe 
PoLystoMELLA.—In its general form this genus resembles | 
the other nautiloid shells above described, but its structure 
differs essentially ; for there are several apertures along the 
side of the shell, as well as the opening in the last segment. 
The cells are simple, and each is a single cavity. The figures 
and details of structure, given by Professor Williamson, 
must be referred to, for an insight into the organization of 
this beautiful and complicated type of Foraminifera.* One 
species of Polystomella is said to occur in the Chalk ; I have — 
not detected this genus in our cretaceous deposits. Recent 
species swarm in our seas; and may be easily obtained from 
the mud and sand on the shores at Brighton.T 
Litvota. Lign. 111, fig. 3a.—In a young state the shell | 
is nautiloid, as in fig. 3b, 3d; but becomes produced by 
age, and assumes a crosier-like form, as in jig. 3a. The cells 
* Trans. Microscop. Society, vol. i. 
+ Mr. Poulton has specimens of the shells, and the bodies of the — 
animals deprived of the shell, mounted for the microscope. 
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