The Autun Boghead possesses practically the same structure. The yellow bodies are often sufficiently abundant to impart a bright yellow colour to a thin section. If the section is vertical the coloured bodies are seen to be arranged in more or less regular layers parallel to the plane of bedding. The Kerosene shale of New South Wales agrees closely with the Scotch and French Boghead; it is approximately of the same geological age, and is largely made up of orange or yellow bodies similar to those of the European Boghead, but much more clearly preserved. The nature and manner of formation of the various forms of coal should be dealt with in a later chapter devoted to the subject of plants as rock-builders, but in view of the recent statements as to the algal nature of these bituminous deposits it may not be out of place to state briefly the main conclusions of the French authors. MM. Renault and Bertrand regard each of the yellow bodies in the European and Australian Boghead as the thallus of an alga. To the form which is most abundant in the Kerosene shale they have given the generic name of _Reinschia_, while that in the Scotch and French Boghead is named _Pila_. _Reinschia._ Fig. 36, 3. A section of a piece of Kerosene shale at right angles to the bedding appears to be made up of fairly regular layers of flattened elliptical sacs of an orange or yellow colour. Each sac or thallus is about 300µ in length and 150µ broad (fig. 36, 3). A single row of cells constitutes the wall surrounding the central globular cavity. The cells are more or less pyriform in shape, and the cell-cavities are filled with a dark substance, described by Renault and Bertrand as protoplasm, and the cell-walls are fairly thick. In some of the larger specimens there are often found a few smaller sacs enclosed in the cavity of the partially disorganised mother-thallus. In the larger specimens the wall is usually invaginated in several places, giving the whole thallus a lobed or brain-like appearance. The supposed alga, which makes up ⁹⁄₁₀ths of the contents of a block of Kerosene shale, is named _Reinschia Australis_; it is regarded by the authors of the species as nearly related to the Hydrodictyaceae or Volvocineae. [Illustration: FIG. 36, 1. Section of a piece of Scotch Torbanite. Slightly enlarged. 2. _Pila bibractensis_ from the Autun Boghead, × 282 (after Bertrand). 3. _Reinschia Australis_, from the Kerosene shale of New South Wales, × 592 (after Bertrand).] In the Kerosene shale from certain localities in New South Wales Bertrand recognises a second form of thallus, which he refers to the genus _Pila_, characteristic of the European Bogheads. _Pila_. Fig. 36, 2. The “thallus” characteristic of the Scotch Boghead has been named _Pila scotica_, and that of the Autun Boghead, _Pila bibractensis_.