[The Squatter of Amon Rûdh]

Here's the scene from the Lay of Leithian in which Beren and Lúthien assume their disguises:

His dreadful counsel then they took,
and their own gracious forms forsook;
in werewolf fell and batlike wing
prepared to robe them, shuddering.
With elvish magic Lúthien wrought,
lest raiment foul with evil fraught
to dreadful madness drive their hearts;
and there she wrought with elvish arts
a strong defence, a binding power,
singing until the midnight hour.

Swift as the wolvish coat he wore,
Beren lay slavering on the floor,
redtongued and hungry; but there lies
a pain and longing in his eyes,
a look of horror as he sees
a batlike form crawl to its knees
and drag its creased and creaking wings.
Then howling undermoon he springs
fourfooted, swift, from stone to stone,
from hill to plain - but not alone:
a dark shape down the slope doth skim,
and wheeling flitters over him.

Or, if you prefer, the version in the Silmarillion is

By the counsel of Huan and the arts of Lúthien he was arrayed now in the hame of Draugluin, and she in the winged fell of Thuringwethil. Beren became in all things like a werewolf to look upon, save that in his eyes there shone a spirit grim indeed but clean; and horror was in his glance as he saw upon his flank a bat-like creature clinging with creased wings. Then howling under the moon he leaped down the hill, and the bat wheeled and flittered above him.

[ October 11, 2003: Message edited by: The Squatter of Amon Rûdh ]