Kevin,

Norman Newell's part of the Treatise on Invertebrate Paleontology (pt. N,
Bivalvia) lists your reference --

1864-1868.  L. Reeve and G.B. Sowerby (eds.) Conchologica Iconica,
Monograph of the genus Unio.  Vol. 16 unpaginated + 96 plates

-- as follows:

Sowerby, G. B., 1864-68, Monograph of the genus Unio: in L. A. Reeve,
Conchologica Iconica, v. 16, 96 pl.

Other parts of the same series are cited as separate works.

Your other questions are more difficult, and I will answer them for a
general audience since I assume other people will have the same problem. In
general, the ICZN allows the dates to be revised later by bibliographic
research, but the authors are as listed in the original work even if that
involves an error in attribution. If the author ascribes a new taxon to
another author, that can be cited as, say, "Forbes in Lyell, 1846". But in
this case, it looks as though Reeve is merely an editor.

The fact that the monograph is dated from 1864 to 1868 suggests that it was
printed and issued in at least 2 parts. In such cases, one may cite the page
numbers as (hypothetically) "p. 1-40, pl. 1-20 (1864); p. 41-60, pl. 21-40
(1865); p. 61-80, pl. 41-96 (1868)" or similar variations. The problem with
bound copies of such books is that people often discarded the half-title
pages on which the dates appeared, keeping only the original 1864 title
page, or perhaps the final title page issued in 1868. Or only one title page
may ever have been issued. Often one has to dig to find the actual
page-by-page and plate-by-plate dates of an early work. And for early works,
if the plate was issued first including a caption, that is the new taxon's
first publication, not the page on which it was described.

Also, with works published at intervals over a period of years, many copies
will be incomplete due to loss in the mail, death of the subscriber, etc.
For example, I have consulted (so far) three copies of Sternberg's rare
masterwork on fossil plants (the starting-point for Linnaean nomenclature of
fossil plants), and keep finding additional pages. I am beginning to wonder
if any complete copies exist.

Bibliographers, historians, and taxonomists have busied themselves by
consulting unpublished correspondence, diaries, and library stamps in order
to determine the dates of the most important older works, and the
information you need has probably already been published. The trick is to
locate the information rather than "reinvent the wheel". That takes some
powerful library resources, or at the least some powerful reference works
such as Biosis, Zoological Record, and a good interlibrary loan department.

Andrew K. Rindsberg
Geological Survey of Alabama