1864.] CARPHNTEK STRUCTUEE OF EOZOON. 63 



examples of the Nummuline type, is here far better displayed than 

 it is in the majority oi fossil Nummnlites, in which the tubuli have 

 been filled up by the infiltration of calcareous matter, rendering the 

 shell-substance nearly homogeneous. In Eozobn these tubuU have 

 been filled up by the infiltration of a mineral different from that of 

 which the shell is composed, and therefore not coalescing with it ; 

 and the tubular structure is consequently much more satisfactorily 

 distinguishable. In decalcified specimens, the free margins of the 

 casts of the chambers are often seen to be bordered with a delicate 

 white glistening fringe ; and when this fringe is examined with a 

 sufficient magnifying power, it is seen to be made up of a multitude 

 of extremely delicate aciculi, standing side by side like the fibres of 

 asbestos (PI. IX, fig. 4) . These, it is obvious, are the internal casts 

 of the fine tubuli which perforated the proper waU of the chambers, 

 passing direct from its inner to its outer surface ; and their presence 

 in this situation affords the most satisfactory confirmation of the 

 evidence of that tubulation afforded by thin sections of the shell- 

 wall. 



The successive layers, each having its own proper wall, are often 

 superposed one upon another without the intervention of any sup- 

 plemental or intermediate sTceleton, such as presents itself in all the 

 more massive forms of the Nummuhne series ; but a deposit of this 

 form of sheU-substance, readily distinguishable by its homogeneous- 

 ness from the finely tubular shell immediately investing the segments 

 of the sarcode-body, is the source of the great thickening which the 

 calcareous zones often present in vertical sections of Eozo'dn. The 

 presence of this " intermediate skeleton" has been correctly in- 

 dicated by Dr. Dawson ; but he does not seem to have clearly dif- 

 ferentiated it from the proper wall of the chambers. All the tubuli 

 which he has described belong to that canal-system, which, as I have 

 shown*, is limited in its distribution to the " intermediate skeleton," 

 and is expressly destined to supply a channel for its nutrition and 

 augmentation. Of this " canal-system," which presents most re- 

 markable varieties in dimensions and distribution, we learn more 

 from the casts presented by decalcified specimens, than from sections 

 which only exhibit such parts of it as their plane may happen to 

 traverse. Illustrations from both sources, giving a more complete 

 representation of it than Dr. Dawson's figures afford, have been 

 prepared from the additional specimens placed in my hands (PL VIII. 

 fig. 5, PI. IX. fig. 5). 



It does not appear to me that the " canal-system" takes its origin 

 directly from the cavity of the chambers. On the contrary, I be- 

 lieve that, as in Calcarina (which Dr. Dawson has correctly referred 

 to as presenting the nearest parallel to it among recent Forami- 

 nifera), they originate in lacunar spaces on the outside of the proper 

 walls of the chambers, into which the tubuli of those walls open 

 externally; and that the extensions of the sarcode-body which 

 occupied them were formed by the coalescence of the pseudopodia 

 issuing from those tubuli f. 



* Op. cit. pp. 50, 51. t Op. cit. p. 221. 



