IN THE ANGLO-PARIS BASIN 115 



Browne was based on a comprehensive knowledge of all the sections then available. 

 Even if they did not consider the detail essential to modern work to be of great 

 importance, they possessed a broader picture than many later workers, some of whom 

 had never examined the sections in the country separated from them by the Channel. 

 Superficially Spath's early stratigraphic work appears to have given far greater 

 precision to the zonation of the Albian, but this was not so. His zonal scheme was 

 introduced without sufficient initial research and suffered greatly by the early need 

 for radical alteration, and in the end his zonal boundaries were ill-chosen. He 

 appears not to have examined the French sections (1943 ; 722-3), which is most 

 unfortunate as it is absolutely essential to have some first-hand knowledge of them. 

 There is no question, however, of the immense value of his contribution. Without 

 his work on the Albian ammonites the progress made in the study of the stratigraphy 

 during the last 25 years would have been very slow indeed. 



Breistroffer (1947) made the first revision to Spath's zonal scheme in an important 

 paper comparing essentially the French with the English succession. In this work 

 he includes the mammillatum Zone in the Lower Albian and the cristatum Subzone in 

 the Upper Albian (1947 ; and Table 2 herein). Casey (1950 ; 270) noted Breistroffer's 

 reading of the mammillatum Zone but followed Spath in including it in the Middle 

 Albian. Khan (1952 ; 73) produced a useful emendation when he included the 

 subdelaruei Subzone in Spath's sense, in the dentatus Zone ; thus placing the junction 

 between the dentatus and lauttis Zones at a point where there is some significant 

 change in the ammonite funa. Casey, however, again followed Spath in terminating 

 the dentatus Zone at the top of the niobe Subzone (1954a ; 264). Milbourne (1956 ; 

 241) could not accept a separate subdelaruei Subzone in Spath's sense. He included 

 the lower part of Bed IV and its lateral equivalents in the niobe Subzone, and the 

 upper nodule bed of Bed IV and its lateral equivalents in the lautus-nitidus Subzone 

 recognising that these probably fell within a distinct Subzone. 



The writer in 1958 reviewed briefly the zonal scheme of the Middle Albian, placing 

 the zonal boundaries at levels where significant changes in the ammonite fauna 

 occurred (1958 ; 160-164). At the same time I drew attention to the difficulties that 

 existed in accepting Breistroffer's emendations of Spath's zonal scheme for the 

 dentatus and lautus Zones ; except for the position of the cristatum Subzone, these 

 have not changed. Subsequently, I proposed formally that the time span repre- 

 sented at Folkestone by the upper nodule bed of Bed IV and the basal few inches of 

 Bed V and their lateral equivalents be recognised as the Subzone of Euhoplites 

 meandrinus (i960 ; 373, 376). The zonal grouping suggested by the author in these 

 two papers is shown in Table 1, p. 10. 



In 1961 Casey produced his important revision of the zonal scheme for the Aptian 

 and Lower Albian (1961a ; 492-499). He now follows Breistroffer in including the 

 mammillatum Zone in the Lower Albian with the exception of Spath's inaequinodum 

 Subzone. For this Subzone he proposes a new index, Hoplites (Isohoplites) eodentatus, 

 and includes it in the dentatus Zone of the Middle Albian, pointing out that this 

 species is the most characteristic ammonite at this horizon in England and France. 

 The division between the mammillatum and dentatus Zones and thus the Lower and 

 Middle Albian now falls at a distinct change in the ammonite fauna. 



