The country between the Wye and the Severn (rivers) was called Ferlys. In Burke, the founder of the 4th Royal Tribe of Wales, was Ethelystan Glodrydd, called "Tributary Prince of Ferlys". His arms are given:
"Quarterly, first and fourth, az three boars' heads cabossed sa. ; second and third, per bend sinister, ermine and erminois, over all a lion ramp. or, which latter was the coat of his mother Rhingor, dau. and heir of Gronwy ap Tudor-Trevor, Lord of Whittington, co. Salop."
[Burke, 1884 ed., p. lxii ]
Quarterly means that the shield is divided into four equal size parts numbered from the upper right. Descent from the father is shown in the 1st and 4th quadrant of the shield, and the material side is shown in the 2nd and 3rd quadrants. Three boars's heads colored black with the heads of the boar looking right forward, full-faced, with nothing of the neck showing. [shield background colored blue]
The maternal side shows a gold colored lion standing upright with a bend [representing a shoulder-belt, or scarf] drawn from the upper left to the right base of the shield. The terms "ermine" means a white field with black spots, and "erminois" a black field with white spots. [representing furs of animals]
The following chart shows this family tree through Tudor Trevor (JC-1).
The eldest son of Tudor Trevor (JC-1) is Gronwy (JD-1) who had Rhingor (JE-3) [daughter and only heir] who was the mother of Ethelystan Glodrydd [Elystan Gloodrydd] (JF-6) the founder of the IV. Royal Tribe of Wales.