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Amphistegina
''Amphistegina'' is a genus of foraminiferal protists included in the Rotaliida with a stratigraphic range extending from the Eocene to recent and a cosmopolitan distribution. The test is an asymmetrically biconvex trochospiral that may be bi-involute or partially evolute on the spiral side. Chambers are numerous, broad. and low, strongly curved back at the periphery to form chamber prolongations. The umbilical side is stellate, like that of ''Asterigerina'', and has a distinct umbilical plug. The wall is calcareous, optically radial; the surface finely perforate and smooth overall. The periphery angular to carinate (keeled); the aperture an interiomarginal slit on the umbilical side, bordered by a lip. Loeblich and Tappan, 1964 included ''Amphistegina'' in the Amphisteginidae along with related ''Boreloides'', ''Eoconuloides'', and ''Tremastegina''; the Amphisteginidae at that time included in the Orbitoidacea, the Asterigerinidae in the Discorbacea. ''Amphistegina'' prefer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphistegina Gibbosa
''Amphistegina'' is a genus of foraminiferal protists included in the Rotaliida with a stratigraphic range extending from the Eocene to recent and a cosmopolitan distribution. The test is an asymmetrically biconvex trochospiral that may be bi-involute or partially evolute on the spiral side. Chambers are numerous, broad. and low, strongly curved back at the periphery to form chamber prolongations. The umbilical side is stellate, like that of ''Asterigerina'', and has a distinct umbilical plug. The wall is calcareous, optically radial; the surface finely perforate and smooth overall. The periphery angular to carinate (keeled); the aperture an interiomarginal slit on the umbilical side, bordered by a lip. Loeblich and Tappan, 1964 included ''Amphistegina'' in the Amphisteginidae along with related ''Boreloides'', ''Eoconuloides'', and ''Tremastegina''; the Amphisteginidae at that time included in the Orbitoidacea, the Asterigerinidae in the Discorbacea. ''Amphistegina'' prefer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |