Vol. 63.^ CARBONIFEROUS ROCKS OF DEVON AND CORNWALL. 



21 



(b) The Plant-Petrifactions, 



At an early stage in the exploration of the western shore-line of 

 Devon, some rolled pebbles, in which small black objects were 

 embedded, were found washed up on the beach. The rock consists 

 of a fine-grained, grey sandstone, in which these bodies are arranged 

 without order. Pig. 2 (below) is reproduced from a photograph of 

 a typical specimen. These pebbles proved to be far from rare, and 



were obviously de- 

 rived from the Upper 

 Carboniferous rocks. 

 The nature of the 

 small, black, lenti- 

 cular structures re- 

 mained somewhat 

 puzzling, until it was 

 noticed that certain 

 of them showed 

 traces of structure. 

 Microscope - sections 

 were then prepared, 

 and it was ascer- 

 tained that they were 

 in reality badly-pre- 

 served plant - petri- 

 factions. This dis- 

 covery was briefly 

 announced in 1904/ 

 and was regarded as 

 of some interest, 

 since petrifactions 

 of Upper Carboni- 

 ferous age, showing 

 the anatomical struc- 

 ture of the plants of 

 that period, are prac- 

 tically confined in 

 England to a single 

 horizon, the Lower 

 Coal Measures of 

 Yorkshire and Lanca- 

 shire. Consequently, 

 a special effort was 

 made to locate the beds from which these pebbles were derived, 

 in the hope that better-preserved specimens might be obtained. 

 It has been found that these impersistent conglomerates are by 

 no means rare, for they occur, here and there, throughout the whole 

 of the Upper Carboniferous Series in Devon and Cornwall. The 

 petrifactions are more abundant in the sandstones, but they are 



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