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 Orbitolites 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. 11), 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 

 Cydoclijpeiis ; 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, very analogous to those which 

 I thought I had discovered in N. lavigata. 



