DESCRIPTION OF THE PLATES. 125 



Given as affording evidences that the gneiss has been methylosed into the 

 hemithrene (pp. 61, 52). The specimens represented under figs. 1, 2, and 3, 

 PL III., are from this quarry. 



Fig. 2. " Eozoon Canadense." A layer of chrysotile in its different stages of 

 development : a, incipient stage ; b, typical chrysotile ; c, closely acicular 

 (" velvet pile ") condition of " proper wall." Canada. 



Fig. 3. " Eozoon Canadense.'' 1 " Proper wall " in two separate laminae, and 

 in different stages of modification. One of the laminae is pectinated, and 

 thus assumes the form typical of the u proper wall." Canada. 



PLATE VII. 



Specimen of a serpentine rock, pseudomorphic after tremolite (natural 

 size). Cannaver, Lough Corrib, Connaught. 



PLATE VIII. 



Specimen of tremolite (natural size), for comparison with that represented 

 in Plate VII., the crystalline structure of both being identical. St. Gothard. 



PLATE IX. (Frontispiece.) 



Fig. 1. Diagrammatic sketch, showing serpentine (a) changing into chry- 

 sotile (b) 5 also the latter in its various modifications or stages of development. 

 Under a the chrysotile is in the (Jirst) incipient stage, being striated ser- 

 pentine (that is, the variety marked with separated thread-like lines or cuts) ; 

 5, (second) fibrous stage, which is typical chrysotile ; c, (third) close-acicular 

 stage, in which the fibres are changed into definite aciculae ; d, (fourth) pecti- 

 nated stage, in which the aciculse are separated by films of calcite thus con- 

 stituting the " proper wall " of " Eozoon Canadense^ 



Fig. 2. Portion, highly magnified, of an accredited specimen of " Eozoon 

 Canadense" showing the different features of the presumed fossil originating 

 from chemical and structural changes in the minerals entering into its 

 composition (pp. 18, 19). The layer a consists of ordinary serpentine 

 changed into the striated variety or incipient chrysotile (a) (other layers 

 consist entirely of structureless serpentine). At b is chrysotile in its typical 

 condition. This layer at top, under c, is changed into the close-acicular variety, 

 and under d into the separate-acicular or pectinated variety, the aciculae in 

 which are separated by calcite : it is thus converted into the tf proper wall " 

 of " Eozoon Canadense" The aciculae in the last stage are considered to be 

 " casts of tubuli," such as characterize the nummuline layer (" proper wall ") 

 of certain recent foraminifers. The letter c denotes flocculite, a white (floc- 

 culent) variety of serpentine, which usually occurs as layers, or clotules : it is 

 often decreted or etched out by solvent action into arborescent configurations 

 (c*), forming the "canal system " of " Eozoon." (N.B. The last'feature is not 

 in its original place : it occurs in another part of the specimen ; but its relations 

 to other eozoonal features are correctly represented.) The layers d (" in- 



