A "-dev" package is supposed to install a "libsomething.so" symbolic link referencing the corresponding shared library. Notice how the link name doesn't include the version number -- this is because such a link is used by the linker when other programs are built against this shared library.
The symlink is generally expected in the same directory as the library itself. The major exception to this rule is if the library is installed in (or beneath) /lib, where the symlink must be installed in the same dir beneath /usr.
Example: If the library is installed in /lib/i386-linux-gnu/libXYZ.so.V, the symlink is expected at /usr/lib/i386-linux-gnu/libXYZ.so.
Implementation detail: This tag is emitted for the library package and not the "-dev" package.