124 DESCRIPTION OF THE PLATES. 



PLATE II. (continued). 



Fig. 3. Portion of a specimen of " Eozoon Canadense" showing a fissure or 

 crack (several more are present in the specimen, see ' Proc. Roy. Irish Acad. 

 vol. x. pi. xli. fig. 4) obliquely intersecting a lobulated layer of serpentine 

 ("chamber-cast;" other layers of the kind are similarly intersected). This 

 fissure, as in other cases, is characterized by " intermediate skeleton " (), 

 bounded at top and bottom by " proper wall " (d). A layer of chrysotile (c), 

 in its incipient stage of development (see PI: IX. fig. 1, a), lies above and in 

 parallelism with the fissure, proving the genetic correlation of the two parts. 

 Observe that the fibres of the chrysotile in the fissure pass continuously 

 lengthwise into the separated aciculee. 



PLATE in. 



Fig. 1. Decalcified specimen, magnified, of saccharoid marble (hemithrene), 

 containing crystalloids of malacolite (a) decreted or etched into branching 

 configurations (a*\ identical with "canal system" of "Eozoon;" also crystal- 

 loids of pyrosclerite (6), some of which have their surfaces coated with aciculae. 

 Mt. St. Philippe, near Marie aux Mines, Vosges. 



Figs. 2 & 3. Crystalloids, highly magnified, of pyrosclerite invested with a 

 fibrous lamina (6), portions of which are pectinated (d), as in the variety of 

 chrysotile corresponding with the " proper wall" of u Eozoon. 1 ' Mt. St. 

 Philippe, Vosges. 



Fig. 4. Section of a crystal of (P)peridote (polarized), associated with ser- 

 pentine. " Eozoon Canadense," Canada. 



Fig. 5. Section of a crystal of (?) peridote (polarized), divided by laminae 

 of calcite corresponding with the cleavage-divisions. The calcite is obviously 

 a replacement product (pseudomorphism). Same as section fig. 4. Canada. 



PLATE IV. 



Ground-plan of a trap-dyke (a) intersecting gneiss (b) in a cove (A) at 

 Glassillaun (B), on the north shore of Cleggan Bay, Connemara. The gneiss 

 is converted into hemithrene (c) in places on both sides of, and adjacent to, 

 the dyke. The dyke is calcitized. 



PLATE V. 



Natural vertical section of the last case (letters the same), showing gneiss 

 converted into hemithrene by action of trap-dyke. 



PLATE VI. 



Fig. 1. Vertical section (being face of a quarry at Mt. St. Philippe) of 

 gneiss (red colour) intersected by irregular masses of hemithrene (green). 



