206 0. HoUedahl — Permian of England. 



mens illustrated in this paper, we are brought to think 

 of all these structures, as do the English geologists,^ as 

 being formed secondarily by very important radical 

 internal changes in the rocks. It has also been pointed 

 out by several of these investigators — and I wish to 

 emphasize this fact — that some of the characters of these 

 structures suggest those developed by crystallization 

 processes. Abbott (1900) points out the likeness of the 

 ''lines'' and ''planes'' in the concretionary beds to the 

 "lines which shoot across congealing water." I might 

 mention especially that the regular right-angle relation 

 between the direction of the concentric and vertical 

 element of the structures seems to be of a similar char- 

 acter to the right-angle relation so commonly seen 

 between the direction of the crystal fibres and the 

 concentric laminae in a laminated crystalline rock, taking 

 as an example a piece of laminated, fibrous, crystalline 

 aragonite like the one the structure of which is indicated 

 in the lower drawing of figure 8, or the well known 

 radiating fibres of calcite (or pyrite which by metasomatic 

 change has taken the place of calcite) in an ordinary lime 

 concretion. 



That the changes in these rocks in general have been 

 great can not well be doubted, and this fact is certainly 

 proved by the English investigators. Yet it is in the 

 residual material of a rock with a cellular structure 

 similar to that which is so common in the Durham 

 limestone that the extremely delicate chains of cells 

 representing parts of blue-green algae were observed. 

 In sections of specimens of Gallatinia pertexta, a "spe- 

 cies" which, as emphasized also by Walcott, is certainly 

 very septaria-like, are reported minute remains of 

 bacteria. This fact may not seem to harmonize very 

 well with the idea of great internal changes in the 

 rock, but we have only to consider how very delicate 

 structures are often preserved in concretions of lime or 

 of silica, where a transportation of mineral matter has 

 also taken place, to realize that the secondary character 

 of the rock and the occurrence of minute cells of plants 

 are not mutually exclusive phenomena. The discovery 

 of algae and bacteria in pre-Cambrian strata, reported by 

 Walcott, has therefore lost none of its importance, even 

 if it should be found that these organisms are not respon- 

 sible for the many curious structures found in the Algon- 

 kian Newland limestone. 



University, Kristiania, October, 1920. 



