GENUS CYCLOCLYPEUS: ORGANIZATION. 555 



probable from the conformation of the shell, that the segments formingsuccessive 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-off. 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, that, 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 both 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-f-, 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 distinguished by a super- 

 ficial examination, especially when young specimens of Cycloclypeus are compared 

 with Orbitolites of the complex type ; since, on the two snrfaces 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 Orbitulite 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 be certainly identical with the A. Boscii of the Paris tertiaries. 



f These are the disks referred-to by Professor WILLIAMSON in his Memoir on Orbitolites, &c., Trans, of 

 Microsc. Soc. ser. 1. vol. Hi. p. 127. He appears to have considered them as gigantic Orbitolites, not being 

 acquainted with their peculiarities of internal structure. 

 MDCCCLVI. 4 D 



