Well, "Henri Ernst"s. ... er, if I asked about this here before, sorry!
Several different Boston publishers (at least two, maybe three? Maybe one publisher under two different names?...) in the 1870s and 1880s or so have arrangements (and perhaps new compositions- need to check) attributed to an "Henri Ernst". I ran into some of these at memory.loc.gov, and so have other editors. Some are listed at worldcat too, i think, and mentioned in books I think but I don't see mention of the basic problem noted below- posthumousness...
Since both Heinrich Wilhelm Ernst- sometimes referred to as Henri - and Henri Ernst the flautist - died in the 1860s - there are several (er- actually, too many) possibilities here, I do think...
(1) a cache of arrangements by Ernst was held onto or found, and published - or reprinted - in the 1870s etc. by these publishers.
(2) a composer whose name was Henri Ernst was the source of these arrangements.
(3) a composer (or more than one) whose pseudonym (self- or publisher- imposed, it matters not) was Henri Ernst was the source of these arrangements.
(actually, several others, some of them very unlikely of course, but even the list of likely and fairly "precedented"/commonly encountered possibilities is still too long.
Question to ask- does anyone know anything about this situation that might clarify, that might have been mentioned somewhere, etc.? Mention of a US-local composer by that name, or anything else that bears on this? Thankee.