Maryland Geological Survey's Bulletin 20, Miocene Fossils of Maryland (by
Harold E. Vokes, John D. Glaser and Robert D. Conkwright, 2nd edition, 2000)
is available as a CD-ROM (for $10 plus $1 postage for US addresses) from the
following address:
http://www.mgs.md.gov/esic/publications/new/b20.html

The only drawback of the electronic format is that the lines that indicated
the actual dimensions of the fossils in the 1957 Vokes edition are not
relevant anymore because apparently the drawings of the fossils were not
scaled according to these lines. So when the dimensions of the plates change
arbitrarily in electronic displays, one cannot tell how long a line was in
the printed version. Unfortunately, the text mentions the actual dimensions
of only a few of the fossils.

Aydin