...The eggshell occurring in the pellets probably was indicative ofextensive feeding on dumping grounds, and I received no reports of eggslost to crows on poultry farms... 
Dwight Platt 「Food of the Crow, Corvus brachyrhynchos Brehm, in South-central Kansas」
...The yolk sac retracts mainly between the time when the eggshell is first punctured and the time when the turtle actually emergesfrom the shell...
John M. Legler 「Natural History of the Ornate Box Turtle, Terrapene ornata ornata Agassiz」
...Eventually the end of the thin brittle priminebreaks like an eggshell and the secundine falls out...
Thomas Mitchell 「Journal of an Expedition into the Interior of Tropical Australia」
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