460 Dr. W. B. Carpenter on Eozoon canadense. 



" The so-called ' nummuline wall ' in Dr. Carpenter's con- 

 structed representation, fig. 2, ought not to be represented in 

 the way it is — bounded by two continuous lines — as it is an 

 integral portion of the grains and plates of serpentine (the 

 so-called ' chamber-casts '), and not a chemically differentiated 

 part like the true calcareous wall of certain Foraminifers." 

 I have represented nothing that my specimens do not dis- 

 tinctly show ; and the only excuse for such an imputation 

 can be, tliat those who made it have never seen the true 

 " nummuline wall," such as I figured it ten years ago, be- 

 fore a question had been raised as to the organic nature of 

 Eozoon (Quart. Journ. Greol. Soc. vol. xxi. plate viii. figs. 3, 4), 

 and such as I now again figure it from a still better specimen 

 in Plate XIX. figs. 1, 2. Professors King and Rowney, 

 merely because they have not met with what I have repre- 

 sented, take upon themselves to deny its existence. 



My true " nummuline wall " is the representative of that 

 which, in recent Foraminifera, immediately surrounds the 

 chambers (PI. XIX. fig. 1, a a). It is 7wt a layer of chry- 

 sotile aciculge ; but is a calcareous lamella, perforated by minute 

 tubuli, which usually lie straight and parallel, but are often 

 more or less curved. These tubuli, like the chambers and 

 canal-system, are usually filled with serpentine, which has 

 passed into them from the chambers in which they originate ; 

 and thus it happens that the original tubulation is generally ob- 

 scured, being only represented microscopically by the differ- 

 ence in refractive index between the calcareous shelly layer 

 and the serpentine which has filled its tubes, — -just as in a 

 specimen of fresh bone or dentine mounted in Canada balsam 

 the tubuli are only represented by the different refractive in- 

 dices of the matrix and the balsam. But in the specimen of 

 Eozoon figured in PI. XIX. figs. 1, 2, many of the tubuli re- 

 main empty ; and they can he distinguished as tubuli under 

 any magnifyiiig-jiower that the thicJaiess of the covering -gla^s 

 allows to he used. Further, they have the somewhat sinuous 

 course of the tubuli of organic structures ; and they present, 

 at what was probably a plane of internipted growth, the 

 sharper flexures which Prof. Owen first pointed out in the 

 tubuli of dentine, and which I described and figured twenty- 

 seven years ago in the hard dentine-like substance of the end 

 of the Crab's claw *. 



That the matrix in which these tubules are channelled out 

 is calcareous^ is shown in this section by the extension into 

 it of the planes of crystalline cleavage (fig. 1, c c) of the " cal- 



* Report of the British Association for 1847, pi. xx. fig. 81. 



