I found, on usenet, the following quote (provided by Dan Clore) from
HOWARD PHILLIPS LOVECRAFT: DREAMER ON THE NIGHTSIDE (1975) in which
Long claims that he ...
> "contributed . . . one forbidden book, John Dee's English
> translation of _The Necronomicon_, which I placed at the
> head of _The Space Eaters_ when that story first appeared
> in_Weird Tales_, but later omitted when the story was
> reprinted in _The Magazine of Horror_, fearing that my
> invention might take on an appalling life of its own and
> appear on the shelves of some unsuspecting and
> defenseless book dealer!"
It would be nice to have the entire quote in context. In any event,
it seems there was indeed an un-cited source, and this is it.
There is of course a problem with the quote, since it seems that at
least part of what it says is not true. The epigraph did not appear
in WEIRD TALES.
Some sources have suggested that Long submitted the epigraph to WEIRD
TALES, but the editor edited it out. I cannot accept this as a
reasonable interpetation of the quote. The only fair reading of what
he is saying is that he SUCCESSFULLY added the story to an earlier
publication (which he mis-recalls as being WEIRD TALES), and then
decided to remove the epigraph in a later revision.
The published history of the tale seems to be as follows:
1928: WEIRD TALES (no epigraph)
1946: THE HOUNDS OF TINDALOS (epigraph)
1963: MAGAZINE OF HORROR (revised, epigraph removed by Long)
1974: TALES OF THE CTHULHU MYTHOS (no epigraph, following the revised
MAGAZINE OF HORROR version).
Apparently the epigraph was later restored in Joshi-era editions of
TALES OF THE CTHULHU MYTHOS
Note that Long does not seem to be saying that the epigraph was part
of the original manuscript of "The Space-Eaters". He mentions it only
as something he added to the tale at time of publication (which, it
turns out, was actually the HOUNDS OF TINDALOS 1946 publication, and
not the WEIRD TALES 1928 publication). Hence, there is no basis for
supposing the epigraph was part of some early manuscript read by HPL
in late 1927 of early 1928.
This does not prevent us from independently crediting Long's claim
that "Dee's NECRONOMICON" was his own invention. HPL and Long
evidently read each others stuff, and probably made suggestions to
each other. This could have been a suggestion provided by Long to HPL
at any time. It is just that there is no reason to connect the
suggestion to the original "Space-Eaters" manuscript.
On the other hand, in light of Long's other evidence of poor memory,
it is hard to rule out the possibility that Long has no independent
recollection of having invented Dee's NECRONOMICON, but merely
concludes that he did because his story was published before HPL's
story, and because others have reached the same conclusion based on
the same logic.