Presidential Address to Section C. 473 



from that of sodium chloride. A consideration of the distances between 

 the atomic centres in crystals supports the conception of the two types of 

 chemical combination. 



13. Mr. David Davies : Palaeontology of the Westphalian 

 and lower part of the Staffordian Series of the Coal-measures as 

 found at Clydach Vale and Gilfach Goch, East Glamorgan. 



Recorded : 43,000 plants; 1,000 shells; two insects and one fish scale. 

 Plants jaelded 154 species, shells six species, insects two species, fish scale 

 one; forty-five of these are newto South Wales and seven new to Britain. 

 Ecology of ten horizons: Equisetales predominate in four, Filicales and 

 Pteridosperms in three, Lycopods in two, and Cordaitales in one horizon. 

 When Lycopods predominate. Fern and Fern-like plants ai'e weak, and 

 vice versa. 37 per cent plants are common to both series ; 31 per cent 

 distinctly Staffordian ; 32 per cent distinctly Westphalian. The Pennant 

 Sandstone produced smooth round coal pebbles, giving evidence of a 

 geological break. A significant feature is the appearance of new species 

 at this period. t 



14. Mr. D. C. Evans : The Ordovician of Carmarthen. 



This paper dealt with the stratigraphical succession and tectonic 

 structures of the Ordovician rocks of Carmarthenshire. 



Presidential Adde-ess to Section C (Geology). 



Owing to unusual pressure on our space we are unable this year 

 to reprint the President's address in full. For the following 

 abstract and appreciation we are indebted to Dr. F. H. A. 

 Marshall, F.R.S. 



Dr. Bather's presidential address deals with the fundamental principles 

 of Palaeontology. He begins by pointing out that it is the time-concept 

 which characterizes the subject and raises it above the mere description 

 of extinct assemblages of animals and plants, and he proceeds to consider 

 the effect of this concept on the principles of classification and on the 

 ideas of relationship. In the light of palaiontological study definitions of 

 groups of animals or plants can no longer be purely descriptive ; they 

 must take account of ancestry and succession in time. As l">r. Bather 

 expresses it : " The old form of diagnosis was per genus et differenliam. 

 The new form in per proavum et modificalionem." It has not been unusual 

 to fall into the error that the apparent succession through a series of strata 

 of similar forms of life implies descent, and Huxley, in his scheme of equine 

 evolution, ves^a,z:AeA PaJceollierium as being in the line of direct ancestrj^ of 

 the modern horse. However, this species, and the leiter A rchitheriuni, have 

 been shown by Professor Osborn and his co-writers to belong to side-lines of 

 descent. Occasionally an apparent succession is due to immigration of 

 a distant relative from another region in the manner supposed by Cuvier 

 in seeking to account for the renewal of life when an earlier fauna had 

 disappeared. Dr. Bather goes on to consider the evidence of descent 

 afforded by palseontological instances of the law of recapitulation, which 

 is so well illustrated by the ammonites. In the next section of the address 

 he points out that the " line upon line " method is the only absolutely 

 safe way of advance in Palaeontology, for mutation must be affiliated with 

 mutation and species with species ; the investigator must work his way 

 back, " literally inch by inch through a single small group of strata," if he 

 wants to be sure of his conclusions about lines of evolution. Concerning 

 the question as to whether descent had taken place by continuous or 

 discontinuous variation it is shown that contrary to what might have been 

 expected, pateontologicai opinion i§ emphatically in favour of the former 



