UTRECHT MICROPALEONTOLOGICAL BUllETINS

very much resemble the comparable elements of Drepanodus arcuatus
PANDER, emend. herein and of Paroistodus amoenus(LINDSTROM). However,
the anterior-posteriorly extended base of the scandodiform elements of
Paroistodus parallelus (PANDER) emend. herein is very characteristic.
Regional occurrence: At Kopingsklint this species occurs from member Kk 2
up to the top of the sequence. In section 6 from member Ka-d 1 to the top of
the section. Near Horns Udde from member Kk 2 up to the top of the Horns
Udde Formation.
Biostratigraphic range: Paroistodus parallelus (PANDER) emend. herein was
found from the Drepanoistodus inconstans Assemblage Zone up to and
including the Triangulodus brevibasis Assemblage Zone (fig. 15).
Genus Period on HADDING, emend. BERGSTROM & SWEET, 1966
Type species: Periodon aculeatus HADDING, 1913.
Definition: "Periodon embraces, multi-element conodont species that include
cordylodus-, ligonodina-, cladognathodus-, roundya-, prioniodina-, and
falodus-like conodont elements." (op cit. Bergstrom & Sweet, 1966,
p.361).
Remarks: According to the emended diagnosis "falodus-like" elements form
part of the multi-element genus Periodon. Instead of "falodus-like" elements
only oistodiform elements, with extended antero-basal edges, were found to
belong to this genus in the Oland material. Therefore, the following addition
to the emended genus definition is suggested: The "falodus-like" elements
may be replaced by oistodus-like elements with an extended and undenticulated
antero-basal edge.
The endings -us-like, used by Bergstrom & Sweet (1966) will be replaced
by -form or by -iform in this paper. The elements of the Periodon 'transition
series, described by Lindstrom (1964, p. 82), will be called the multiramiform
elements.
Periodon flabellum (LINDSTROM), emend. LINDSTROM, 1971
(PI. 4, figs. 14-20)
Trichonodella flabellum LINDSTROM, 1955a, p. 599, PI. 6, figs. 28-3b.
Periodon flabellum (LINDSTROM). LINDSTROM, 1964, p. 83, figs. 28 A-D.
Periodonflabellum (LINDSTROM), emend. LINDSTROM, 1971, p. 57, fig. 18.
Prioniodina? deflexa LINDSTROM, 1955a, p. 586, PI. 6, figs. 31-35
Prioniodina inflata LINDSTROM, 1955a, p. 588, PI. 6, figs. 26, 27.
o;.lodus inflatus (LINDSTROM). LINDSTROM, 1964, p. 85, figs. 30 A-B.
Oistodus selene LINDSTROM, 1955a, p. 580, Pi. 4, figs. 19,20.