I'm afraid that Paul is right, as he has a habit of bieng, when he
points to Americain Seashells, vol. ii, as not being one of Tucker's
finest moments!!  I know the man is like a small-g god in the
Conchological World, and many of his books are quite excellent.  He was
most familiar with Western Pacific molluscan fauna, and did a LOT of
splendid science in that field.  However, when it came to many areas of
North America, he was simply "out of his element", and to be frank, did
not seek the aid of enough regional experts when working on the book.
Also, it was a bit of a "rush job" - i don''t know the details, but for
some reason the final copy was not carefully proof-read, and tons of
typos and switched plates were the result. That said, it is nevertheless
a monumental effort, and the only attempt at a complete treatment of
North Americain molluscs, and we are better off having it than NOT
having it!!
        Jim Harasewych at the Smithstonian is currently working on v.iii, but
it will be a while, since he is a busy man to begin with, and so much
work has been done in the past 25 years that the task is nothing short
of incredible!!  He is a very careful worker, and the final work will be
as good as it gets, science-wise, and i'm certain he will consult with
folks like Jim McLean and Scott and Coen, who both have major monographs
on the West Coast fauna (gastropods and bivalves, respectively) in the
works.  Scott and Coan's long-anticipated bivalve book for the entire
West Coast of N.A., should be out by Feb, with a bit of good fortune!!
I think the hardest part will be my neck of the woods (E.Canada and the
Gulf of Maine), where marine molluscan taxonomy is long stagnant - the
Turrids alone are a total nightmare (trust me on this one!!! - they
represent 10% of our total fauna also, so this is not "trivial"!), the
Buccinids need a good revision, many habitats such as deep-water coral
communities, deep basins, fjiords in W. NFLD, etc., are scarcely touched
sample-wise,  etc....  It may be another century at least before what
could be called a truly "comprehensive" work on E. coast molluscan fauna
is possible (or maybe some billionare will come along and throw some Big
Bucks our way!! - lets all send shells to Bill Gates :-)  ).
-Ross.