Vol. 63.] CARBONIFEROUS ROCKS OF DETOX AND CORNWALL. 17 



V. The Fossil Flora and the Horizon of the Beds. 



As already stated, the chief object of this enquiry was to discover 

 the horizon of the highest beds of the Upper Carboniferous Series 

 as developed in Devon and Cornwall, by an examination of the 

 fossil plants which they contain. It has also been pointed out that, 

 .although the rocks are everywhere greatly disturbed, and therefore 

 the working-out of the original sequence of the deposits is practically 

 impossible, there is reason to believe that the highest beds are those 

 which occupy roughly the centre of the trough. 1 



So far as I can distinguish, these beds, as seen in the coast- 

 section, differ neither in lithological aspect (see p. 5) nor in 

 palseontological facies, from those, developed nearer the edges of 

 the basin, which underlie them. It has been seen that the goniatites 

 and other marine invertebrates occurring in calcareous nodules are 

 •distributed practically uniformly throughout the Upper Carboniferous 

 sequence in Devon and Cornwall. Such plant-remains as it has 

 been possible to obtain from the beds occupying the centre of the 

 basin have proved to be species common in the Middle Coal 

 Measures, the horizon to which the Bideford beds also have been 

 shown to belong. 2 Unfortunately, the number and preservation 

 of the specimens leave much to be desired. Although fragments 

 of plant-remains are often extremely abundant, and of common 

 occurrence, it is rare to find a specimen, or fragment, sufficiently 

 well preserved to permit of specific identification. In fact, the task 

 of obtaining a representative flora from these rocks proved well nigh 

 hopeless, and such examples as have been procured are the result of 

 much labour, and continuous search spread over many weeks. 



Of the thousands of ill-preserved fragments that I have seen, I 

 have never found one which in the least recalled any of the typical 

 Upper Coal Measure plants. All the evidence, so far as it is 

 trustworthy, points to the conclusion that the highest 

 beds to be found in the Carboniferous basin of Devon 

 and Cornwall belong to the Middle Coal Measures.' 



(a) The Plant-Impressions. 



The following impressions have been obtained from localities 

 which are believed to be situated on higher beds than those found 

 in the Bideford district. 



Catamites SucJcowi, Brongn. and Calamocladus equisetiformis 



1 The general extent of these beds is roughly indicated in Mr. Ussher's 

 recent map (Ussher [01J pi. xvi), where they are shown uncoloured but with 

 a fine hatching, and are marked C 5 in the index to the Map. They form the 

 Upper Culm Measures in Mr. Ussher's classification. 



* Arber (04) p. 316. 



3 This horizon is termed the ' Westphalian ' by Mr. Kidston, (05) p. 319, 

 in his revised terminology for the zones of Upper Carboniferous age, founded 

 on palaeobotanical evidence. I regret, however, that I am unable to adopt the 

 new terms proposed, for several reasons, among which I may mention the use of 

 the term Westphalian, which has long been employed on the Continent 

 in a far wider sense than that now adopted by Mr. Kidston. 



Q. J. G. S. No. 249. c 



