32 PROCEEDINGS OE THE COTTESWOLD CLUB 



forms of life are, I shall show that at times they lived in 

 great profusion in the depths of the sea, and there 

 performed a work of incrustation around nuclei which 

 became a considerable factor in the formation of the 

 calcareous deposits and subsequent Hmestone rocks. 



Shortly stated, the process which went on in the 

 Silurian sea during the formation of the Wenlock limestone 

 was this : the shells and skeletons of the larger marine 

 organisms which existed collected on the floor of the sea 

 in very small fragments. Whether this condition was 

 due to detrition or to the fact that the creatures had 

 served as food for large Ganoid fishes, I know not. 

 Judging, however, by the high percentage of inorganic 

 detrital material in the Wenlock limestone derived from the 

 denudation of existing rocks, which sometimes amounts 

 to as much as 30'4 per cent., I conclude that land was 

 not far distant. Consequently the Wenlock Limestone 

 represents a Terrigenous deposit, and the shells, etc., 

 would probably be subject to the action of waves. This 

 may be an cxpl.maLijn of the fragmentary condition in 

 which they occur in the Wenlock limestone. 



These remains having finally settled on the floor of 

 the sea, then the incrusting process of Girvanella 

 commenced. Tubules of this genus attached themselves 

 to fragments of debris as nuclei, and partially or entirely 

 enclosed them in a crust formed by the multiplication 

 and growth of the tubules. 



To avoid misunderstanding I must make it clear that 

 there are very many exceptions to the fragmentary 

 conditions of the shells and other calcareous remains of 

 organisms which have furnished material for the building 

 up of the Wenlock limestone. Thus it is not difficult to 

 find well preserved portions of coral, especially of 

 polyzoa, shefls, etc. These fossils, however, in the May 

 Hill district of Gloucestershire, are chiefly to be found 

 in argillaceous beds which separate thin strata of limestone. 



