|Geographic Location||Datong Dist., Taipei City|
|Dimension||L. 14 cm; W. 9.4 cm|
This piece of shell, identified as Cristaria discoidea, was unearthed from a historic layer of Dalongdong site, Datong District, Taipei City. The Cristaria discoidea of Cristaria, Unionidae is commonly known as “green mussel” or “ridged mussel” in Mandarin, as it has a dark brown color with a green shade. The inner side of the shell has a shiny pearl tint. Only one side of the bivalve shell was found, it has an apparent ridge on the back. The hinge teeth and the ventral side of the shell are broken. It is an edible mussel which can be found in varied habitats including river, pond and paddy fields.