Pirate Treasure Motif-index
Some of the motifs from OI common to other treasure stories include:
1) stone slab atop the treasure's resting place
2) box slipping away or vanishing
3) indecipherable inscription
4) accidental discovery of the site
5) tapping on the chest/box just before disaster strikes
6) site noticed by child, not by adults
7) guardian (OI: the flood tunnels/water trap)
8) breaking the spell causing loss of the treasure (OI: going to church, tapping on the still-buried chest before uncovering it.)
Something I need to think about: the "going to church = loss of treasure" idea might have other implications. I have a sense that since the treasure represents avarice (greed), perhaps the church attendance represents "the devil's revenge," in the respect that the men are punished for not completing the "evil" work of pursuing earthly gain. I seem to recall there are numerous examples of this motif in other tales, but I'm away from my references right now.
Other motifs that appear common include:
1) use of ritual to uncover treasure:
a) divination
b) not speaking during excavation
c) reading of scripture to ward off "guardians"
d) digging only at night
2) guardians
a) dead pirates
b) "large black man" executed and buried atop the treasure
c) demons/imps
d) witches
e) other supernatural forces
3) person watches treasure being buried
a) dies before recovering it
b) is not believed by others until it's too late (Peter & the Wolf?)
c) thinks to keep it for himself, repents on deathbed
i) dies before disclosing location
ii) discloses insufficient detail to permit recovery (OI: sailor's tale)
d) is unable to locate it later on
Also see: www.mysteriousbritain.co.uk/folklore/craig-y-ddinas.html