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RATTRAYELLA. 49 1
GENUS 153. RATTRAYELLA. DE TONI. 1889.
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Valves circular, plain in
the median portion, then
gently convex towards the
margin, very finely punctate,
with puncta arranged in
radiating
lines and often
covered with a kind of
vague network. Margin
showing small processes,
rounded or elliptic, between
each of which is one or
two apiculi.
Fig. iT&.Rattrayella
This genus only comprises
Oatr.arucnsis. a single species. B . Oamcirilensis
(Grun.), De Toni, found in the fossil deposits of Sysran, Simbirsk and
Ananino (Russia), as well as in the deposit of Oamaru. The figure in the
text (fig. 22S), is drawn from one of my photographs.
Fig. 229.
Cestodiscus Pr
GENUS 154. CESTODISCUS GREV.. 1865.
Valves disciform, circular, oval, rarely angular,
granular, with granules arranged in radiating
rows, furnished with round or elongated tubercles,
forming a complete circle, near the margin of the
valve.
This genus only comprises a small number o*
species, the greater part being fossil. I include in my
generic diagnosis Trkeratium cinnamomeum Grev., which should, perhaps,
form a special genus.
The figure in the text (fig. 229), represents Cestodiscus Proteus Hard-
man, after an authentic example of the author. Mr. Rattray
Cestodiscus, Perithyra, and Micropodiscus among the Coscinodiscus.
classes the