The 1st and 2nd printings of this manual contained the Cthulhu and Elric Mythos. Later editions did not include these.
What happened was that Chaosium held the rights to both of these properties. Chaosium actually granted TSR these rights retroactively and are thanked in the second printing of the book on page 4. However, the Blume brothers did not like thanking Chaosium in print so had the two offending chapters removed for the third printing. However, the thank you wasn't removed until the fifth printing.
According to Frank Mentzer at GenCon SoCal 2003, the printings of this book were referred to internally at TSR as follows:
1st: Squids, no thanks!
2nd: Squids with thanks!
3rd and 4th: No squids with thanks! (3rd has wizard logo, 4th has face logo)
5th: No squids, no thanks!
6th and later: Legends & Lore (ok, so Frank didn't mention this part, but the 6th printing is when it changed titles)
The problem with this is that it does not line up with TSR's own printing info in the books, as the second iteration of Legends & Lore actually said "6th Printing" on the title page. All the versions prior didn't list any printing info. The most likely explanation is the 1st and 2nd are actually the same printing. It has been said that 1st printing was stopped midway through and the thanks inserted (by order of Brian Blume no less). This is further detailed here: http://www.hahnlibrary.net/rpgs/faq/rgfdfaq4.html#E8. Frank Mentzer implied there were only four printings in the discussion at GenCon SoCal, but did not say so one way or the other directly.