ii 4 MIDDLE ALBIAN STRATIGRAPHY 



Spath produced a scheme of ammonite horizons which foreshadowed the zonal scheme 

 which appeared the following year (1922 ; 96) . He was far too critical of the previous 

 work on the Albian and certainly misread Jukes-Browne, and so in 1923 he dis- 

 carded the broad zonal classification of previous workers in favour of the scheme 

 shown in Table 2. This zonal scheme was strongly influenced by the sequence at 

 Folkestone which Spath had examined in detail (1923a ; 73 : 1923b ; 4 : and see also 

 1923c). Unfortunately, in England the sequence between the ' mammillatus Zone ' 

 and the 'dentatus Zone ' was at that time very imperfectly known. The ' inaequin- 

 odus Zone ' formed a very uncertain taxon, and the ' benettianus Zone ' was par- 

 ticularly ill-founded for Spath had no idea of the exact stratigraphical position of the 

 lyelli fauna (1923c : 142, see 1926b ; 422), and he was later to classify even high 

 spathi Subzone sediments with that Subzone. De Ranee had already used the term 

 ' benettianus Zone ' in a different sense, and it is unfortunate that Spath ignored the 

 sequence in the southern part of the Paris Basin. In effect he restricted the dentatus 

 Zone to exclude much of what the French workers understood by this term. He also 

 discarded Jukes-Browne's lautus zone replacing it with zones of intermedins, delaruei 

 and cornutus, but added a cristatus zone for Bed VIII and its lateral equivalents. 

 It was unfortunate that this scheme should have been presented before Spath had 

 fully studied the species he had used as indices. In the following two years he had 

 to alter this zonal scheme (1924 ; 505 : 1925b ; 31-36), and the year after (1926b ; 

 421-2, 425) saw the extensive modification shown in Table 2 (p. 116). 



In 1926 Spath first renamed the lower part of his cornutum Zone, the Zone of 

 Euhoplites alphalautus (1926a ; 154 footnote 1), and then later recognised that this 

 species was a form found in the varicosum Zone. The major change in the scheme 

 given by him later that year (1926b ; 421-2, 425) was the relegation of his zones to 

 the rank of subzones in the Table on p. 421. However, the presentation shows 

 several inconsistencies for he refers to these subzones in the text as zones. In the 

 table he groups the subzones into the ' old zones ' which are in fact those used by 

 Jukes-Browne, the names being corrected where necessary. Spath included the 

 intermedins Subzone in the dentatus [ohm interruptus] Zone, but Jukes-Browne had 

 in fact included Bed II at Folkestone in his lautus zone. Spath recognised, however, 

 that the zonal schemes which had been used in Europe were of provincial value only, 

 and this was a significant step forward. 



The zonal scheme was further modified during the course of publication of successive 

 parts of Spath's Monograph, and one saw the firm readoption of the broader zones. 

 He formally presented the various emendations to his earlier scheme in 1941 (1941 ; 

 668) and discussed them briefly the following year (1942 ; 671-673) : these are given 

 in Table 2. His ' zones ' of 1923 are now emended and reduced to the status of 

 Subzones which are grouped into three Zones. The mammillatum Zone is much the 

 same as that of Barrois and Jukes-Browne, however, the dentatus and lautus Zones 

 do not correspond with the views of earlier workers despite Spath's comment (1942 ; 

 672 footnote 3). Is the arrangement given by Spath an improvement ? The junction 

 between the dentatus and lautus Zones was placed by Spath at a level where there is 

 no significant change in the fauna and the arrangement is quite arbitrary. 



The older zonal grouping of French and English workers such as Barrois and Jukes- 



