| 1. | For storage and road transport the wings folded at two hinge lines.
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| 2. | The rear of the elevators at the rudder hinge line.
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| 3. | The Pentamerida, Terebratulida, Atrypida and Athyridida have narrow hinge lines.
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| 4. | The hinge line is not as short as found in the Rhynchonellida or Athyridida.
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| 5. | There is a small, partly faired sprung tailskid immediately ahead of the rudder hinge line.
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| 6. | Like the ligament, the hinge teeth are also situated along the hinge line of the shell.
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| 7. | This kind of hinge line is also found in the bivalve families Glycymerididae, Nuculidae and Nuculanidae.
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| 8. | Terebratulids are also distinguished by a very short hinge line, and the shell is punctate in microstructure.
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| 9. | The Orthida and Spiriferida have wide hinge lines where the two valves ( or shells ) articulate.
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| 10. | Bivalves by definition have two ligament situated on the hinge line at the dorsal edge of the shell.
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