Ubuntu font package fonts-lyx
You can install these fonts by opening a terminal and executing sudo apt-get install "fonts-lyx"
See also: installing software on Ubuntu, installing software on debian, and general fonts-lyx package information.
cmex10
cmex10 font family with style Normal/usr/share/fonts/truetype/lyx/cmex10.ttf
cmmi10
cmmi10 font family with style Normal/usr/share/fonts/truetype/lyx/cmmi10.ttf
cmr10
cmr10 font family with style Normal/usr/share/fonts/truetype/lyx/cmr10.ttf
cmsy10
cmsy10 font family with style Normal/usr/share/fonts/truetype/lyx/cmsy10.ttf
eufm10
eufm10 font family with style Normal/usr/share/fonts/truetype/lyx/eufm10.ttf
msam10
msam10 font family with style Normal/usr/share/fonts/truetype/lyx/msam10.ttf
msbm10
msbm10 font family with style Normal/usr/share/fonts/truetype/lyx/msbm10.ttf
rsfs10
rsfs10 font family with style Italic/usr/share/fonts/truetype/lyx/rsfs10.ttf
stmary10
stmary10 font family with style Normal/usr/share/fonts/truetype/lyx/stmary10.ttf
wasy10
wasy10 font family with style Normal/usr/share/fonts/truetype/lyx/wasy10.ttf