That's an interesting result and some of the entries point up a major
frustration for bibliographers, which may be shared by some scholars. A
number of those entries are reprints of pieces under new names, and others
are excerpts from his books. It's sometimes fun and instructive (but more
often tedious and pointless) to trace a Twain piece (sketch, quote, speech,
interview, review, whatever) from its first newspaper appearance, to its
first magazine appearance, and finally to its first book appearance,
although they seldom go through every one of these stages, or follow this
sequence. And it's also sometimes worthwhile to trace a particular piece of
writing as it spread around the country or the world under various titles
and with nonauthorial deletions (and even additions) that reflect the
culture and the times.
Now if you want a real challenge, begin with BAL and Greg Camfield's "Oxford
bibliography" and trace each entry...
Kevin Mac Donnell