1866.] GUMBEL — ON LATJRENTIAN ROCKS. 101 



of serpentine with curved and undulating outlines, resembling the 

 Eozoon ophicalcite of Canada. The etched portions show, in the 

 carbonate of lime between the serpentine, or in the interspaces of 

 the serpentine, the same relations as the limestone of Hohenberg 

 from the primitive clay-slate formation. The tubuli, which have 

 a certain resemblance with those of Hohenberg, are stuck together, 

 as if covered by an incrustation. Further examinations of this 

 limestone are required to determine more definitely the organic 

 nature of its enclosures. 



A fragment of similar limestone without serpentine, from 

 Raspenau, shows not the remotest trace of any organic structure 

 whatever. The same negative results were obtained with a 

 specimen of granular limestone from Timpobepa in Brazil ; and 

 with a very coarsely crystalline carbonate of lime, holding 

 chondrodite, from Amity, New Jersey. These negative results 

 show that organic remains are sometimes wanting in the primitive 

 crystalline limestones, as well as in those of more recent for- 

 mations. The occasional absence from the primary limestones of 

 these regular structures is therefore an indirect argument for 

 their organic origin. 



Explanation of the Plate. 

 Figure 1. Section of Eozoon Canadense, with its serpentine replacement, 

 showing the fine tubuli and the canal-system, from the limestone of 

 the Hercynian gneiss formation at Steinhag ; seen by reflected 

 light, and magnified 25 diameters. 



2. Section of Eozoon from the limestone of Untersalzbach; 25 diameters. 



3. Section of Eozoon from the limestone of Babing. 



4. Section of Eozoon from the limestone of Steinhag ; 120 diameters. 



5. a and b. Knotted tubuli from the insoluble residue of the Steinhag 



limestone ; 300 diameters. 

 (5, a, 1), c, and d. Flocculi from the same residue ; 400 diameters. 



7. Section of Eozoon Bavaricum, with serpentine, from the crystalline 



limestone of the Hercynian primitive clay-state formation at 

 Hohenberg ; 25 diameters. 



a. Sparry carbonate of lime. 



b. Cellular carbonate of lime. 



c. System of tubuli. 



d. Serpentine replacing the coarser ordinary variety. 



e. Serpentine, and hornblende, replacing the finer variety, in the 



very much contorted portions 



8. Aggregated grains of pargasite, remaining after the solution of the 



carbonate of lime, from the granular limestone rock of Parga*. 



