For the publication of Gould's
The birds of Australia, see Zimmer 1926
https://biodiversitylibrary.org/page/36194906. This work was published in 36 parts, most of which consisted only in plates and their associated text; the "general" matters -- 7 title pages for the 7 final volumes, the introduction, index, binding directions, etc. -- came with the last part (36). Publication started in Dec 1840 and ended in Dec 1848; four parts were published yearly, on 1 Mar, 1 Jun, 1 Sep and 1 Dec, except that the last 4 parts (33-36) were all published at once on 1 Dec 1848 (i.e., 7 parts in total, instead of the usual 4, were published in 1848). The publication sequence departed completely from the sequence adopted in the bound volumes; external information is necessary to find out the date associated to a particular plate. Waterhouse 1885
https://biodiversitylibrary.org/page/12782739 gives a list of the plates with the part to which it initially belonged, and the year of publication.
Gallinula tenebrosa was indeed published in part 22, presumably as the 14th plate in this part, which is what "Birds of Australia part 22 plate 14, 1846" indicates. (Although this type of citation is certainly useful for historical and dating purposes, it is indeed potentially confusing to someone actually trying to locate the description...) Part 22 was the first part issued in 1846 according to Zimmer, thus the date is 1 Mar 1846.
Gould presented all the species he illustrated in
The birds of Australia before he published the plates, usually at meetings of the Zoological Society of London, and his descriptions were published in the
Proceedings of that Society. However, due to delays in the publication of some of these, in some cases the corresponding plate and text of
The birds of Australia was published first, and the name then dates from them. The dates that appear in the
Proceedings (such as the "Feb 24, 1846" that you cite) are the dates of the meetings -- not dates of publication. The dates of delivery (= publication) of the
Proceedings between 1830 and 1859 were published by Sclater 1893
https://biodiversitylibrary.org/page/35992702.
Gallinula tenebrosa also appeared in: Gould J. 1846. Descriptions of eleven new species of Australian birds.
Proc. Zool. Soc. London, 14: 18-21.; p. 20;
https://biodiversitylibrary.org/page/12862670. According to Sclater, this dates from May 1846.
March being before May, the book has precedence in this case.
Gould J. [1840-]1848.
The birds of Australia. In seven volumes. Vol. VI. Published by the author, London. Plate 73 and text (published in part 22, 1 Mar 1846).
https://biodiversitylibrary.org/page/48400878
