Setting font to Lucida Grande on Mac OS X

[Sancho Neves-Graca]

I am running Emacs 21.3.50 Carbon Mac OS X 10.2.6.

I would like to change the font of a frame from the default (Monaco) to 
the system default (Lucida Grande). For other fonts which are named by 
a single word the following commands work:

M-x set-frame-font RET -*-Monaco-*-120-*
M-x set-frame-font RET -*-Courier-*-120-*
M-x set-frame-font RET -*-Helvetica-*-120-*

But the command

M-x set-frame-font RET -*-LucidaGrande-*-120-*

returns Font '-*-LucidaGrande-*-120-*' is not defined.

What is the name known to Emacs for Lucida Grande? If a space is 
needed, how is it entered (pressing Space returns [No Match])?

Further, what entry in ~/.MacOSX/environment.plist is necessary to set 
this new font as the default for any new frame?