98 Mr. E. A. Newell Arber. Fossil Flora of the [May 30, 



It may be also noticed that there would seem to be a tendency at 

 the present time in certain quarters to regard the Culm Measures 

 as essentwlly a Lower Carboniferous series of deposits. Professor 

 Hull's* (1881) opinion that "the flora of the 'culm'" belongs "to 

 the Lower Carboniferous series of Devonshire" is a case in point. 

 This view is not, however, shared by all British geologists. It has 

 arisen partly from the fact that the older literature has to some 

 extent been lost sight of, and partly from the great interest aroused 

 by the work of Messrs. Hinde and Fox, which has brought into 

 special prominence that portion of the Culm Measures which is of 

 Lower Carboniferous age. We have also in recent years gained a 

 more intimate acquaintance with the flora of the so-called " culm " 

 or " kulm " of Germany, Austria, and elsewhere on the Continent ; 

 deposits of Lower Carboniferous age, as shown by 'the character of 

 their fossil remains. 



In recent years we have come to know more of the distribution of 

 fossil plants in the Coal Measures of this country, chiefly as the 

 result of Mr. Kidston's researches, and it is now possible to distinguish 

 clearly a certain number of horizons in the Upper Carboniferous. 

 During Upper Carboniferous and Permian times, periods which belong 

 to the same botanical epoch, the general character of the flora in its 

 broad outlines remained constant. Yet detailed study has shown that 

 it is possible to detect the gradual changes which took place during 

 this interval, and the underlying principle of zoning the Carboniferous 

 system depends upon the recognition of definite periods in which 

 these changes became more marked. Thus the general character 

 of the flora of the Bideford district is identical with that found 

 elsewhere in Britain in Middle Coal Measure times. The majority 

 of the species recorded here are known to occur in both the 

 Middle and Lower Coal Measures. But there are also others, such as 

 Alethopteris Serli, and Calamocladus charceformis, which are unknown 

 from the Lower Coal Measures, and others again, such as Sigillarm 

 tessellata and Neuropteris obliqua, which are markedly more abundant in 

 the Middle than the Lower Coal Measures. In other words, the 

 change in the general character of the flora of the Upper Carboniferous, 

 as traced from the base to the summit, is already marked on this 

 horizon by the presence of species which are not found in the lower 

 beds. On the other hand, there is an entire absence of certain genera 

 and species, especially of the genus Pecopteris, which are character- 

 : m this country of higher horizons such as the Upper Coal 

 Meaning. Thus the horizon in the Upper Carboniferous represented by 

 *ai portion of the Upper Culm Measures in which the coal or culm occurs in 

 I district is equivalent to the Middle Coal Measures in other 



* 'Coal Fields of Great Britain,' 4th ed t., p. 64. 



