UTRECHT MICROPALEONTOLOGICAL BUllETINS

totally fused. The denticles are erect to reclined and subcircular in cross
section. The bases of the first two denticles are somewhat elevated above
those of the succeeding denticles. The first one is fused to the cusp. The
antero-basal process is long and slightly sinuously curved. It carries some
denticles, which are fused to the process on their posterior sides. The basal
cavity intrudes both processes as a shallow groove. It is roughly triangular in
side view and the oral and anterior outlines are both straigth. The aboral
margins of the posterior and anterior processes make an angle of about 80°.
Where they meet there is a bulge in the aboral margins on both sides of the
unit. Fine striation is present all over the cusp and the anterior proc~ss.
The gothodiform element (PI. 6, fig. 3) is quite similar to the prioniodinaform
element, it only has a lateral costa to one side of the cusp. This costa
forms an undenticulated, short and free process where it meets the aboral
margin.
The oepikodiform element (PI. 6, fig. 4) has two lateral costae but
otherwise it is quite similar to the prioniodinaform element. The costae form
two short and undenticulated processes where they meet the aboral margin.
The roundyaform element (PI. 6, fig. 5) has a proclined cusp. Its cross
section is subcircular at the top. Downward there are two faint lateral costae,
which gradually pass)nto the lateral processes. These are well developed and
carry some subequal, straight and' almost entirely fused denticles. The
posterior process is straight and has a similar denticulation as 'the prioniodinaform
element. The basal cavity extends as a very shallow groove into the
processes. .
The falodiform element (PI. 6, fig. 6) has a blade-like and reclined cusp.
At the boundary of the anterio~ edge of the cusp and the anterior p~ocess
there is a very faint inflection. The denticles on the anterior process are
almost entirely fused. The basal cavity extends into the processes as shallow
grooves. It has already been figured by Pander (1856, PI. 3, fig. 7) and by
Lindstrom (1955a, PI. 5, figs. 21, 22, 30). Pander called his specimen
Prioniodus carinatus but most probably the holotype of that form species
does not belong to the multi-element species under consideration, because
the denticles on the anterior process of the holotype of Prioniodus carinatus
PANDER (1856, PI. 2, fig. 25) are not fused. According to Lindstrom
(1955a, p. 569) this falodiform element would have been described by
Graves & Ellison (1941) as Oistodus prodentatus. In the bland material,
however, the anterior edge of the cusp and the anterior process are almost
straight and reclined, in contrast with the specimens figured by Graves &
Ellison.
Regional occurrence: Not reworked remnants of this species were only found