546 



Supplementary Note. 



[Read 28th February, 1870.] 



Within the last fortnight we have been successful in finding "eozoonaT 7 

 structures under conditions which unmistakeably establish their origin. 



We have first to notice a specimen of ordinary metamorphic micro- 

 crystalline limestone, from Aker, in Sweden. It contains numerous 

 light green grains of pyroxene of the variety known as coccolite, a 

 considerable portion of a colourless translucent variety of a related 

 mineral seemingly malacolite, and a few small purple spinels. The 

 grains of coccolite, which have a rude cleavage approximating to a sub- 

 conchoidal fracture, are isolated, or form aggregations, in the calcareous 

 matrix : their surfaces are variously rounded and excavated, giving the 

 grains an irregularly lobulated appearance. The occasional presence 

 of planes, edges, and solid angles on their surfaces, renders it certain 

 that the grains were originally crystals that have undergone super- 

 ficial erosion by some dissolving agent. The spinels, which are in 

 octahedrons, have been subject to a similar waste, though not to the 

 same extent — only occasionally occurring more or less spherical, and 

 with eroded surfaces. 



In their irregular lobulated character, variety of aggregation, and 

 scattered arrangement, the grains of coccolite strikingly resemble those 

 of serpentine (" chamber casts") in the " acervuline" variety of 

 " Eozoon Canademe" occurring in Canada. We take credit for being 

 the first to point out a precisely similar agreement in the grains of 

 chondrodite, pargasite, &c, common in the crystalline limestones of 

 other places.* 



But the specimen under notice shows other and additional characters, 

 which still more clearly establish its " eozoonal" relationship. 



When a slight portion of the matrix is removed by decalcification, 

 the surface is seen to be crowded with slender cylindrical forms, more 

 or less branching, often remarkably beaded, and arranged in all con- 

 ceivable modes of grouping. They agree in every respect with the 

 finest typical examples of the " canal system," as represented by Doctors 

 Carpenter, Dawson, and Professor Rupert Jones. f 



Associated with the latter are numerous specimens of the malacolite, 

 divided by different sets of cleavage planes, the principal one giving 

 them quite a lamellar structure. Occasionally others occur, approxi- 

 mating more or less to perfect prismatic crystals : but generally some of 

 the angles, edges, and planes, have disappeared, or only traces are 

 observable ; so that they present the appearance of vermicular rods — 



* "Quarterly Journal of Geological Society," vol. xxii., p. 209. 



f See Dawson in " Quarterly Journal of Geological Society," vol. xxi., PI. VII., 

 figs. 3, 4, 5 ; Carpenter, ibid., PI. VIII., fig. 5, a, b, c, and PI. IX., fig. 5, a, b, c, d ; 

 Eupert Jones, " Popular Science Review," vol", iv., PI. XV., figs. 6, 7, 8. 



