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Amphisphaera goruna (Sanfilippo and Riedel, 1973)

Description - Add description

Cortical shell ellipsoidal, of variable wall thickness, with
pores subcircular or occasionally rosette-shaped, of irregular size and
arrangement (distance between centers approximately 9-17.5μ). From
the surface of the cortical shell arise several strong, blades spines -
commonly a long one at or near each pole (its length approaching that
of the cortical shell) and 1-3 shorter ones scattered over each half-
ellipsoid. Medullary shell single, delicate, pyriform, with its axis not
aligned with the longer spines (and therefore commonly appearing to be
circular in outline). Cortical and medullary shells joined by six or more
radial bars, some of which are collinear with some of the external spines.
In the older assemblages examined, many specimens have no medullary
shells nor internal bars.

Measurements:
(based on 20 specimens from 86-7, CC; 86-8, CC;
and 96-3-1). Major diameter of cortical shell 65-105μ, its minor diam-
eter 60-95μ. Width of medullary shell 25-35/u.

Remarks:
This species is distinguished principally by possessing two
or more strong spines on each half-ellipsoid. Excluded from the present
definition are rare specimens resembling Stylosphaera coronata but with
two spines at one pole and one at the other (Plate 25, Figure 11), and
a small, single-shelled ellipsoidal form having sparse, irregularly dis-
tributed pores and a group of thorns at each pole (Plate 25, Figure 12).
The specific name is an arbitrary combination of letters, used as a
noun in apposition.





Sanfilippo and Riedel 1973


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