560 DR. CARPENTER'S RESEARCHES ON THE FORAM1NIFERA. 



direction. Still their continuity is maintained through all the successive layers of 

 which even the thickest part of the shelly disk may be composed. 



106. Besides the radial and vertical systems of canals, there is an annular system, 

 which traverses the thick band of shell-substance that usually intervenes between the 

 successive annuli, and which is continually brought into view in horizontal sections 

 (Plate XXIX. figs. 10, 12). It appears from vertical sections traversing the annular 

 septa, that several tiers of these annular canals may exist. I have frequently traced 

 them running continuously for a considerable distance, without appearing either to 

 give off any branches, or to communicate with the radial canals; but I have occa- 

 sionally seen appearances which indicate that such a communication is established 

 by means of canals passing vertically downwards at the angles of the chambers, so 

 as to unite the three sets of canals into one continuous system, furnished with a mul- 

 titude of orifices upon the surface of the disk. A representation of the whole canal- 

 system, as I believe it to exist in this organism, is given in Plate XXX. fig. 4. 



107. The uses of this canal-system can only be a matter of speculation. Not having 

 had the opportunity of examining specimens in which the soft animal substance had 

 been preserved, I am unable to affirm whether the interseptal canals of Cyclodypeus 

 are occupied in the living state by a portion of the sarcode-body, or whether they are 

 empty ; but as I have unquestionable evidence that the former is the case in Poly- 

 stomella, I should think there can be little doubt that it is also true of this genus. 

 Now if we come to examine the purpose of this canal-system, we are at once struck 

 with the fact, that it can scarcely be requisite for the nutrition of the segments of the 

 sarcode-body enclosed within the chambers; since the mutual communication which 

 these segments have with each other, seems fully as adequate for the purpose in 

 Cyclodypeus, as it is in Orbitolites, Orbiculina, or Alveolina. If we examine wherein 

 this organism so differs from the foregoing as to require such an additional system, 

 we may find a not improbable answer in the possession of that additional skeleton 

 which intervenes between the proper walls of the chambers ; for the canal-system, 

 excavated in the very substance of this, would seem to furnish the appropriate chan- 

 nel for its nutrition. And that such is its object, will be shown in a future memoir 

 to be almost certainly proved, by the comparison of facts then to be adduced from 

 the structure of other genera. 



108. Monstrosities. Although the number of specimens of this type which I have 

 had the opportunity of examining is but small, yet two among them exhibited the 

 same kind of monstrosity as that which is common in Orbitolites ; namely, the super- 

 position of a vertical plate upon the horizontal disk (Plate XXX. fig. 3). And in each 

 it is sufficiently apparent that this plate has originated from the central cell, and that 

 its increase has taken place pari passu with that of the horizontal disk. 



109. General Summary. If, now, we review the principal facts relating 'to the 

 structure of Cyclodypeus, and compare them with those furnished by Orbitolites on 

 the one hand and by Nummulites on the other, we shall see that, notwithstanding 



