A. J. Jukes-Browne— The Subdivisions of the Chalk. 249 
arrangement may indeed be regarded as practically a division of the 
formation into three parts, viz. the Chalk without flints, including 
the Chalk Marl; the Chalk with few flints; and the Chalk with © 
many flints. 
Phillips was content with this terminology, but Woodward went 
much further, and gave greater distinctness to the divisions by indi- 
cating their extent on his map, by recording the fossils found in 
each, and by proposing a more convenient nomenclature. 
Subsequent geologists, however, who described the Chalk in the 
South of England, Mantell, De la Beche, and Dixon, do not seem to 
have appreciated the truth conveyed in Woodward’s nomenclature, 
and only recognized two divisions above the Chalk Marl, viz. a 
Lower Chalk without flints, and an Upper Chalk with flints. This 
classification, though apparently more simple, is not necessarily more 
natural, but being adopted by the majority of writers, it finally 
found its way into Manuals of Geology, and into the publications 
of the Geological Survey. 
Between the Upper and the Lower Chalk, however, no clear line 
of separation was recognized until 1861, when Mr. Whitaker de- 
scribed a particular bed under the name of Chalk Rock, and indicated 
its occurrence at the top of the Lower Chalk in the counties of 
Wilts, Berks, Oxford, and Bucks. He acknowledged, moreover, the 
occasional presence of flints in the Lower Chalk, and proposed to 
regard this rock as forming a convenient line of division between 
the Lower and Upper Chalk. ; 
Mr. C. B. Rose deserves mention as the only geologist who 
followed in Woodward’s steps ; he always maintained the expediency 
of adopting the arrangement into Lower, Medial, and Upper Chalk, 
and pointed out that in Norfolk certain fossils are characteristic of 
each division. Mr. Gunn also made a point of this in his Geology 
of Norfolk (1864). 
Until 1870, however, very little was added to our knowledge of 
the distribution of organic remains in the Chalk. During that year 
Mr. Caleb Evans published a paper on “Some Sections of Chalk 
between Croydon and Oxtead”; this was a contribution of much 
value, because the author had carefully collected the fossils from 
each set of beds, and was the first to perceive the possibility of a 
zonal classification for the English Chalk. He establishes six of 
these subdivisions or zones, and groups them under three headings, 
v1z.— 1. The Chalk, with bands of flint. 
2. The Chalk, with bands of Marl. 
3. The Grey Chalk and Chalk Marl. 
—thus reviving the older tripartite arrangement, supporting it by 
paleontological facts, and so placing it on a firmer basis. 
Dr. Barrois’ work, published in 1875, and entitled ‘ Recherches 
sur le Terrain Crétacé Supérieur de l’Angleterre et de l’Irlande,” is 
now well known to all students of the Chalk, and has already been 
brought before the notice of this Society. I need only observe, 
therefore, that Dr. Barrois applies to the English Chalk the same 
zonal classification which has been so carefully worked out in France 
