David Lloyd Blayney 
BLAZON OF ARMS:
Sable, three nags' (or horses') heads erased argent.
On a wreath, a nags's (horse's) head couped argent, maned and tufted sable bridled gules, on the forehead a piece of armour with a projecting spike proper.
Two horses Sable, with bridles, saddles andhoofs or
REF: Family Name History [PO Box 428 Buddina, QLD, Australia 4575].
or Universal Historical Dictionary 
This is the same as the arms of King Brochwel Yagythrog which were "[Sable] three nags' heads, erased [argent]" and represented the Saxon white horses, with their heads severed, and symbolised his victory over the Saxons in 564 A.D. [See Brochwel]
Arms & Crest of the Irish Lord Cadwallader Blayney, (9th Baron):
ARMS: [Diamon] three horses heads erased, [pearl].
CREST: On a wreath, a horse's head couped, [pearl], bridled, [ruby], having his forehead covered with armour, and a spike in the midst like that of a target, proper. [Rhydderch, John "Pedigrees of Montgomeryshire families, selected about the year 1711-12 from Lewis Dwnn's original visitation" (London: Whiting & Co, 1888)]
The Blayneys of London:
ARMS: [Sable] a trefoil [or] between three horses' heads erased [argent].
CREST: a horse's head, couped, [argent], in complete armour ppr., bridle, [azure].