UTRECHT MICROPALEONTOLOGICAL BUllETINS

Regional occurrence: At Kopingsklint this species occurs from a level at
about 1.50 m. above the base of the Bruddesta Formation up to the top of
the sequence. In section 6 from a level at about 1.70 m. above the base of
the Bruddesta Formation up to the top of the section. Near Horns Udde
from a level at about 2.10 m. above the base of the Bruddesta Formation up
to the top of the Horns Udde Formation.
Biostratigraphic range: Microzarkodina flabellum was found from the Microzarkodina
flabellum Assemblage Zone up to and including the Triangulodus
brevibasis Assemblage Zone (fig. 15).
Genus oelandodus n. gen.
Type species: Oistodus elongatus LINDSTROM, 1955.
Derivatio nominis: After Oland.
Definition: A multi-element genus with oistodiform (after Oistodus
PANDER emend. LINDSTROM, 1955a), elongatiform (after Oistodus elongatus
LINDSTROM) and triangulariform (after Oistodus triangularis
LINDSTROM) elements.
Differential diagnosis: The only multi-element genus for which this genus
could possibly be mistaken is Oistodus PANDER, emend. VAN WAMEL
herein, from which genus it differs in having an elongatiform element instead
of a deltaform element.
Oelandodus elongatus (LINDSTROM), emend. VAN WAMEL, herein
(PI. 7, figs. 1-4)
Description: In the original description of Oistodus elongatus Lindstrom's PI.
4, figs. 32, 33 represent our elongatiform element, his fig. 5b the triangulariform
element.
The oistodiform element has not been described yet.
To Lindstrom's description of the elongatiform element the following can
be added (see PI. 7, figs. 1,2):
In lateral view the outline of the basal cavity is rounded. Its tip is bent in
antero-basal direction and it is situated at the place where two lateral costae
or carinae have their origin on the base. The keel of the oral edge is evenly
convex outwards.
The cusp is very wide and flat. Its posterior keel can have a faint sinuous
curvature. The angle between the oral edge and the posterior keel varies
between 70 0 -100 0 • The whole unit is usually slightly bent sidewards. The