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One is on the left light of St. John the Baptist Preaching by William Morris located in The Lady Chapel. The second is in the centre of The East Wall decoration at the top.
In he Middle Ages people believed that the pelican fed its young from spots of blood plucked from its own breast. This became an allegorical depiction of Jesus Christ, in both His sacrificial love and resurrection. In an age when literacy was limited, the image of the Pelican-in-her-Piety would have been recognisable and understood by everyone who saw it and was, in particular, interpreted as being symbolic of the Eucharist.
Thomas Aquinas used the allegory in his 'Adoro Te Devote'
"O loving Pelican! O Jesu Lord!
Unclean I am but cleanse me in Thy Blood of which a single drop,
for sinners spilt,
can purge the entire world from all its guilt."
From great medieval cathedrals to small churches across Europe the image of the Pelican-in-her-Piety is a very Catholic symbol. The brass lectern in Durham Cathedral is an excellent example..