182 THALLOPHYTA. [CH. 



In addition to the Bogheads of Autun, Torbanehill, and 

 New South Wales, there are similar Palaeozoic deposits in 

 Russia, America, and various other parts of the world. Full 

 details of the structure of Boghead and the supposed algae 

 referred to Reinschia, Pila, and other genera will be found in 

 the writings of Bertrand and Renault \ 



The Kerosene shale of New South Wales affords the most 

 striking and well-preserved examples of the cellular orange and 

 yellow bodies referred to as the globular thalli of algae. It is 

 almost impossible to conceive a purely inorganic material 

 assuming such forms as those which occur in the Australian 

 Boghead. On the other hand, it is hardly less easy to 

 understand the possibility of such explanations as have been 

 suggested of the organic origin of these characteristic bodies. 



The ground-mass or matrix of the Boghead is referred to a 

 brown ulmic precipitate thrown down on the floor of a Permian 

 or Carboniferous lake, probably under the action of calcareous 

 water. In this material there accumulated countless thalli of 

 minute gelatinous algae, which probably at certain seasons 

 completely covered the surface of the waters, as the fleurs d'eau 

 in many of our fresh-water lakes. In addition to the thalli of 

 Reinschia and Pila the Bogheads contain a few remains of 

 various plant fragments, pollen-grains, and pieces of wood. 

 Fish-scales and the coprolites of reptiles and fishes occur in some 

 of the beds. On a piece of Kerosene shale in the Woodwardian 

 Museum, Cambridge, there are two well-preserved graphitic 

 impressions of the tongue-shaped fronds of Glossopteris Browni- 

 ana, Brongn. There can be little doubt that the beds of 

 Boghead were deposited under water as members of a regular 

 sequence of sedimentary strata. The yellow bodies which form 

 so great a part of the beds are practically all of the same type. 

 Reinschia and Pila cannot always be distinguished, and it 

 would seem that there are no adequate grounds for instituting 

 two distinct genera and referring them to different families of 

 recent algae. 



Stated briefly, my conclusion is that the algae of the 



^ Bertrand (93), Bertrand and Renault (92) (94), Bertrand (96), Renault (96). 

 Additional references may be found in these memoirs. 



