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GENUS 170.
Fig. 254.
b
Stictodiscus.
a. S. Kittoniatius fgirdle faceJ.
/'. 5. Johnsonianus (valve).
STICTODISCUS.
STICTODISCUS GREV., 1861.
Valve disciform or angular,
with median portion inflated,
inflation unequal in the two
valves ; centre more or less
hyaline ;
the remainder of the
valve more or less strongly
punctate, puncta arranged in
radiant rows, separated by
plicae.
This beautiful genus includes about 50 species, the greater number of
which are fossil. In the text will be found, after Greville, the valve of S.
Johnsonianus Gr., and the girdle face of S. Kittonianus Gr. These two species
are fossil, the first is found in the Naparima deposit (Trinity Island), the second
in the deposits of South America, specially Nottingham, Richmond, &c.
GENUS 171. ARACHNOIDISCUS EHR, 1849.
Fig. 255.
Arachnoidiscus ornatus.