Perhaps you're looking for this one?
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/09/30/INSL1LAQ9R.DTL

On Sat, Jan 28, 2012 at 10:54 AM, Tracy Wuster <[log in to unmask]> wrote:
> Hello all,
>
> I am preparing for an upcoming talk, and I am hoping to find one of two
> illustrations to use as a visual.
>
> The first is from the London Hornet from December 13, 1873 in a story
> called "Mark Twain on Woman."  It features a frog with the head of Mark
> Twain.  There is a copy in Scrapbook #12 at the Mark Twain Papers, but I
> have been unable to find a scan of it.
>
> The second is from the New York Graphic, from September 21, 1874, also
> showing Mark Twain as a frog.  This illustration is found in Lou Budd's, *Our
> Mark Twain*, on page 53.
>
> If anyone has a useable scan of either of these, I would be tremendously
> grateful.
>
> Best,
>
> Tracy Wuster