192 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Jan. 10, 



fibres are easts of tubules, how could such be the case in places 

 where the asbestiform layer, as just noticed, consists of intimately 

 juxtaposed fibres, with nothing between them* ? Por anything that 

 we observed to the contrary, the fibres thus circumstanced displayed 

 quite as little evidence of having been parietally separated as those 

 of asbestus. Moreover the fibres " sometimes pass oif obliquely or 

 even tangentially, so as to run for considerable distances in the 

 chamber- walls," — a peculiarity which, as it has "no parallel" 

 among foraminifers, we were disposed to accept as negative evidence 

 against their foraminiferal origin. 



These facts and considerations produced in us in the early stage 

 of our investigations simply a scepticism as to the organic origin of 

 the asbestiform layer. Entertaining no doubt regarding Dawson's 

 view of the other structures, we were merely led to suspect that this 

 part was the product of crystallization. 



Subsequently our suspicion became a settled conviction on dis- 

 covering examples of the " proper wall " under circumstances which 

 clearly showed it to be altogether independent of the " calcareous 

 skeleton." The conclusion just stated we hold to be demonstrated 

 by the example represented in fig. 2, Plate XIY., than which nothing 

 can more intelligibly explain the purely crystalUne origin and nature 

 of the part in question. This remarkably beautiful example, selected 

 out of a number of the same kind, is taken from an undecalcified 

 slice of Grenville Ophite t : it consists of three or four closely con- 

 joined granules of serpentine (a plate of slightly individualized 

 " chamber- casts "), having on one side a continuous border of 

 "proper wall," which, when examined with a sufficiently high 

 power, is seen to have, for the most part, a perfectly compact 

 asbestiform or indefinitely fibrous structure; while in two places 

 (a and h) this structure is in an incipient state of development, 

 consisting of a number of parallel thread-like lines clearly and 

 somewhat widely separated: the one kind passes into the other. 

 That it is no other than the serpentine thus crystallized is rendered 

 evident by the lines in the part marked h being extended only 

 partly" across the width of the " proper wall," leaving, without a 

 shadow of doubt, a narrow external zone of the mineral devoid of all 

 traces of lineation immediately in contact with, but plainly distinct 

 from, the "calcareous skeleton." If, in this case, the "proper 

 wall" had been originally calcareous, like the " skeleton," as main- 



* In Nummulina IcBvigata we find the width of a parietal interstice between 

 two adjacent tubules to slightly exceed their diameter ; so that casts of the tu- 

 bules would, if their walls were dissolved out, be separated by strongly-defined 

 linear openings. Possibly it may be suggested that the " appearance of a minute 

 prismatic arrangement " which nummulines occasionally display, and which is 

 conceived to have been produced by "metamorphosis" or " fossilization " (see 

 Carpenter, Quart. Journ. Geol. Soc. vol. vi. p. 25, and ' Introduction to the 

 Study of the Foraminifera,' p. 270), explains the compact fibrous structure of 

 the "proper wall" of ^^ Eozoon Canadense •," but this is obviously too unsatis- 

 factory a case to be of any assistance, it being merely one of ajppearance, which 

 is possibly in some measure due, as believed by Dr. Carpenter, to the " areola- 

 tion" of the "tubules," similar to what prevails in Operculma. 



t Our other examples are generally decalcified. 



