and on the half-title we find
The Ring of the Niblung a trilogy with a prelude
by Richard Wagner translated into English
by Margaret Armour. I.
so we combine and adapt the two titles, as
Wagner, Richard. The Ring of the Niblung;
transl. by Margt. Armour; illus. by Arthur
Rackham. I. 1910
I, The Rhinegold. The Valkyrie.
and give the usual references
Armour, Margaret (Transl.) See Wagner,
Richard.
Rackham, Arthur (Illus.) See Wagner, Richard.
"Transl." is a perfectly clear abbreviation for either translated or translator—the shorter form, "tr.", may mean anything, and is to be avoided.
Later still we get another book, the principal entry for which is
Barrie, Jas. M. Peter Pan in Kensington Gardens;
illus. by Arthur Rackham. 1910