GENUS CYCLOCLYPEUS : — ORGANIZATION. 
555 
probable from the conformation of the shell, that the segments formingsiiccessive bands 
do not communicate directly with each other so much as with the great longitudinal 
stolons ; just as the successive annuli of superficial cells in Orbitolites communicate 
with each other, not immediately, but through the annular stolons 28). The 
pseudopodial prolongations issuing from the marginal orifices, probably first coalesce 
into a longitudinal cord of sarcode, when a new band of cells is to be formed ; and 
from this another series of segments is then budded-olF. — In the texture of the shell, 
in the relations of the different chambers, in their mode of communication with the 
exterior, in all (to speak concisely) which marks the physiological condition of this 
organism, its conformity to the types previously described is so close, tliat, notwith- 
standing the marked difference in their mode of increase (on which depends their 
form), they must rank, in any natural classification, in very close proximity with 
these*. 
Genus Cycloclypeus. 
95. The organisms which 1 have now to describe, and to which I shall give the 
generic designation Cycloclypeus (suggested to me by Dr. J. E. Gray), are amongst 
the most interesting of all the Foraminifera at present existing; on account botli of 
the large dimensions which they sometimes attain, and also of the complexity of their 
structure. The only specimens of them yet known, were dredged by Sir Edward 
Belcher from a considerable depth of water off the Coast of Borneo. Two of these, 
which are now in the British Museum'l-, are complete disks measuring no less than 
2 ^ inches in diameter ; and by the kindness of Dr. J. E. Gray, I have had the oppor- 
tunity of making microscopic sections of a fragment of a disk, which, when entire, 
must have nearly equalled these in size. Smaller disks of various dimensions pre- 
sented themselves in the same dredgings. 
96. Organization. — The external aspect of these disks is sufficiently like that of 
Orbitolites, to prevent the two genera from being readily distinguishetl by a super- 
ficial examination, especially when young specimens of Cycloclypeus are compared 
with Orbitolites of the complex type ; since, on the two surfaces of the former 
(Plate XXX. fig. 1), there can be distinguished concentric rings of oblong cham- 
bers, which are not at all unlike the similarly-disposed superficial cells of the latter. 
The peculiarly-compact texture of the shell of Cycloclypeus, however, gives to its sur- 
face a smooth and glistening appearance, which is very different from that of Orbi- 
tolites. And further, the forms of the two disks ordinarily differ in this, — that whilst 
the centre of Orbitolite is usually rather depressed than elevated, and the thickness 
* I have confined myself to an account of the existing species, as I have not had the opportunity of making 
a similar examination of any large number of fossil forms of this type. It is well, however, for me to mention, 
that the existing species seems to me to he certainly identical with the A. Boscii of the Paris tertiaries. 
t These are the disks referred-to hy Professor Williamson in his Memoir on Orbitolites, &c., Trans, of 
Microsc. Soc. ser. 1. vol. iii. p. 127. He appears to have considered them as gigantic Orbitolites, not being 
acquainted with their peculiarities of internal structure. 
4 D 
MDCCCLVI. 
