Prof. Garwood — Calcareous Algce. 441 



Since then I have examined a large numher of nodules collected 

 from different horizons in the Lower Carhoniferous rocks of Britain 

 and Belgium, and the examination has convinced me that the remains 

 of Calcareous Algae play a very much more important part in the 

 formation of these rocks than has hitherto been generally realized. 



The majority of geologists in this country have been slow to 

 recognize the importance of these interesting organisms, and, with the 

 notable exception of Sir Archibald Geikie's textbook, we find but 

 scant allusion in English geological works of reference to the important , 

 part played by Calcareous Algse in the formation of limestone deposits.^ 



From the more strictly botanical standpoint, however, we are 

 indebted to Professor Seward for an admirable account of the forms 

 recognized as belonging to this group up to the date of the publication 

 of his textbook on Eossil Plants in 1898 ; while in an article in 

 Science Progress in 1894 he has also dealt with their importance 

 from a geological point of view. 



Since these publications, not only have several new and important 

 genera been discovered in this country and abroad, but the forms 

 previously known have also been found to have a very much wider 

 geological and geographical range than was formerly suspected. For 

 these reasons I venture to hope that a summary of our knowledge of 

 the part they play as rock-builders, more especially in British deposits, 

 will serve to stimulate an interest among geological workers in this 

 country in these somewhat neglected organisms. 



Previous to 1894, in which year Dr. Brown first referred Solenopora 

 to the I^ullipores, with the exception of the Jurassic and Tertiary 

 Characeae, we meet with little, if any, reference to the occurrence of 

 fossil Calcareous Algse in British deposits. 



Indeed, in this country the subject has attracted but few workers, 

 and they can almost be counted on the fingers of one hand. When 

 we have mentioned the late Professor H. A. Nicholson and 

 Mr. Etheridge, jun., Mr. E. Wethered, Dr. Brown, Dr. Hinde, and 

 Professor Seward, we have practically exhausted the list of those who 

 have contributed to our knowledge of the subject. To these we may 

 add the name of Mrs. Robert Gray, whose magnificent collection of 

 fossils from the Ordovician rocks of the Girvan district has always 

 been freely placed at the disposal of geological workers, and has 

 furnished numerous examples of these organisms to Professor Nicholson 

 and the officers of the Geological Survey. 



It was Nicholson and Wethered who first recognized the important 

 part played in the formation of limestones by certain organisms, which, 

 though referred at the time to the animal kingdom, are now generally 

 considered to represent the remains of Calcareous Algse. 



The presence of these organisms in a fossil state, especially in the 

 older geological formations, has only been recognized in comparatively 

 recent years; though it was suggested as long ago as 1844 by 

 Forchhammer- that fucoids, by abstracting lime from sea water, 

 probably contributed to the formation of Palaeozoic deposits. When 



1 Geikie, Textbook of Geology, 4th ed., vol. i, pp. 605, 611, 1903. 

 '^ British Association, 1844, p. 155. 



