UTRECHT MICROPALEONTOLOGICAL BUllETINS

formities in the rock-sections. By recording the elements of the multielement
species separately, the boundaries of the conodont assemblage zones
tend to be accentuated. The boundaries of the assemblage zones were drawn
at the base (boundaries defined on first appearances) or at the top (boundaries
defined on disappearences) of fossiliferous samples, and not within the
barren intervals.
The distribution of the conodonts indicates that no clear correlation exists
between the occurrence of any conodont species and a certain rock-type.
Evidently, the conodonts were rather independent of environment within
the area of study. The assumption that conodont species had a wide
distribution allover the area and that assemblages of similar composition
were of about synchronous origin therefore seems justified.
This enables the establishing of the chronological sequence of all conodont
assemblages within the area. The ultimate succession of the conodont
assemblage zones, given in fig. 15, made it possible to reconstruct the ranges
of the conodont species in the regional rock-sequence.
In the composite range chart of fig. 15, the arrangement of the conodont
species from left to right corresponds with the order of their first appearances
in the regional rock-sequence. Species that appear simultaneously were
arranged according to length of deduced ranges, the species with the shortest
ranges being entered first. The reader may be shocked by the inflation in
zonal names, based on one or a few samples, especially in the lower portion
of the column. After long and serious consideration the author thought it
preferable to enter into extreme splitting. The predominance of gaps in the
basal portion of the record over intervals really represented by rocks is
apparent from the considerable differences in faunal succession in the lower
portions of the three sections. As a consequence it is considered probable,
that every observed notable difference in faunal composition might stand for
a longer period, that is worth a separate zone. After all it is better, if
necessary, to lump some of the present zones on the basis of more continuous
sections, found in future work, than to neglect considerable differences
in faunal composition. To lump now the zones we recognized would
give the resulting zones a distinctly heterogeneous character from one
section to the other.
Chart V illustrates the regional extent of the conodont assemblage zones,
according to their presence in sections 1, 6 and 14. The assemblage zones
found in the three small rock-sections of the Djupvik Formation at Kopingsklint
(fig. 4) were placed below section 1. Section 9, containing the Cordylodus
angulatus/G.prion Assemblage Zone, was placed below section 6. The
rock-section studied at locality 2 (see fig. 5) near Horns Udde and its
constituent assemblage zones were placed besides section 14.