Kyd karhwine morva
Llyfr Du Caerfyrddin XXXIV

Kyd karhwine morva. cassaue mor
Pyr toei wanec carrec camhur.
Glev diwal hygar hael huyscur.
Yscinvaen beirt bit butic clydur.
Goruc clod heilin benffic awirtul.
Kyd carhiuwe morua cassaaue ton.
Digones ton treis oer cleis y ron.
Ew kuynhiw iny wuiw in hervit hon.
Gweith heinyw golchiw ar winvywron.
Kid y lleinv keudaud nis beirv calon.
Ac inllvrv kyheic kiniod y ron.
Yssim edivar oe negessev.
Ban wrissuis pebrur pell y aghev.
Glev diwal kyweithit yd vam in dev.
Menic it arwet duwir dalennev.
Fechid diristan othiwod.
Mi nythervill imchod.
Omparth guertheisse march irod.
Dial kyheic amoet blis.
Am y kywrev y melis.
Och corr dy sorrde ymi bv ewnis.

Version from the Myvyrian Archaiology:

Gwyddneu Ai Cant

Kyd karui vi Morva, kassaa vi mor pur
Doe waneg karrec kamhur
Glew diwael hygar hael hwyskur
Yscinvaen beirt bid bydic clydur
Goruc klod Heilin benffic awirdwl
Hyd braud parahawd y ertivul
Hyd karui vi Morfa cassa vi don
Digoneis don dreis oer kleis y ron
Ef kwyniw yn i wiw herwyt hon
Gwaith heiniw golchiw or winuiuron
Kyd illeinw keudaud nis beirw kalon
Ac ni lluru cyheic kumod y ron
Y vun edivar oi negessau
Ban vryssyus pebrur pell y agheu
Glew diwal kywerthyd yd vain in de u
Menic it arwet duwir dalenneu
Fechit dirisclan oth divot
Mi nith erwill fuched diot
Om parth gwerthais y march irot
Dial kyheic amoed blis
Am y kyvreu y melis
Oth korr dy sorr di ymi bu ewnis

Why the poem is identified with Gwyddno is obscure; perhaps the references to the sea lead the editors to asign it to the legendary king. However, there is no basis for this. In fact, Rachel Bromwich asigns the poem not to the stories of the Cantre'r Gwaelod, but to that of Trystan.