According to Parker:
Griffin, or Gryphon, (fr. griffon): the Griffin is the most frequently represented of the imaginary animals introduced into coats of arms. Although variously drawn, the great principle is that it is a compound of the Lion and the Eagle. The lower part of its body, with the tail and the hind-legs, belong to the lion; the head and the fore-part, with the legs and talons, to those of the eagle, but the head retains the ears of the lion. It has large wings, which also closely resemble those of the eagle. Its ordinary positions are rampant segreant(generally blazoned segreant only), and passant segreant.
It may be represented as without wings, and then with rays or spikes of gold proceeding from several parts of its body. Sometimes it has two long straight horns. The term Alce is given, as if used by writers for a kind of griffin, but no example can be quoted…
Griffins’ heads are also represented in some coats. They are readily distinguishable from the eagles’ heads by the presence of the ears.
The Opinicus is allied more nearly to the dragon in the forepart and in the wings; but it has a beaked head and ears, something between the dragon and the griffin. The hind part and the four legs are probably intended to represent those of a lion, but the tail is short, and is said to be that of the camel.