GENUS CYCLOCLYPEUS : — ORGANIZATION. 
559 
105. I have now to speak of another feature in the structure of this organism, 
which most strikingly differentiates it from OrhitoUtes and its congeners, and at the 
same time furnishes an additional proof of its close approximation to Nummulites, 
notwithstanding the difference in its plan of increase. I allude to the system of 
interseptaL canals, which establish a direct communication between the external sur- 
face, and the parts of the interior most removed from it. Such radial canals are seen 
both in horizontal and vertical sections (Plate XXIX. fig. 10, Plate XXXI. fig. 4, c) 
excavated in that shelly substance, which occupies part of the space that intervenes 
in the radiating partitions between the proper walls of adjacent chambers of the 
same annulus. When the canal reaches the end of the radial septum, it usually sub- 
divides into two, which diverge at a considerable angle from each other, so as, by 
traversing the annular septum, to reach the two alternating radial partitions of the 
next annulus ; and as each branch, before entering the partition towards which it 
runs, unites with another branch that inclines towards it from the radial canal next 
adjacent, it follows that just as every chamber communicates (normally) with the 
two alternating chambers in the annuli internal and external to it, so do the inter- 
septal canals of every radiating partition communicate with those of the partitions 
alternating with it in the internal and external annuli. This arrangement, which 
cannot be described verbally without some complexity, will be readily comprehended 
by an inspection of Plate XXIX. fig. 11. In each radial partition there are at least 
two, and very commonly three tiers of such canals, as is best seen in vertical sections 
that cross the radial partitions transversely (Plate XXXI. figs. 4, 5). Short trans- 
verse branches, apparently communicating with the cavity of the chambers (Plate 
XXIX. fig. 1 1), are sometimes seen to proceed from the longitudinal canals ; in regard 
to these communications I would not speak with confidence from what I have seen in 
Cycloclypeus ; but that they exist in other organisms, hereafter to be described, is un- 
questionable. There can be no doubt, moreover, that the horizontal radiating canals 
communicate with vertical canals which pass directly towards the two surfaces of the 
disk, whereon they open (Plate XXXI. fig. 5, c) ; these canals are best seen in hori- 
zontal sections taken near the upper or under surfaces of the chambers (Plate XXXI. 
figs. 3, 9), in which they present themselves in regular rows, d, d, corresponding to 
the radial partitions ; whilst in similar sections taken nearer the surface, they are seen 
to be less regularly disposed, in consequence of their following a somewhat oblique 
in the process of fossilization. I was led to this by the very marked contrast which exists in Nummulite be- 
tween the tubular, and non-tubular portions of the shell, and the peculiarly inorganic semi- crystalline appear- 
ance of the latter, closely resembling that of the calcareous infiltration which usually occupies the interior of 
the chambers. Subsequent examination, however, of Nonionina and other recent forms most closely allied to 
Nummulite, has satisfied me that these columns were part of the original shell, as my friend Professor William- 
son maintained from the first. It is not a little curious, however, that in certain other species of Nummulite 
described by MM. D’Archiac and Haime, a system of passages should exist, verj'^ analogous to those which 
I thought I had discovered in N. laevigata. 
