Answer: Clonorchis sinensis /Opisthorchis sp. eggs
The characteristic features of these distinctive eggs are their small size (19-35 micrometers in length), 'urn' shape, shouldered operculum and abopercular knob:
The eggs of Opisthorchis sp. are slightly smaller than those of Clonorchis sinensis, but there is significant overlap and it is not usually possible to differentiate the two.