It is rare that you need to specify a font name in Emacs; usually you specify face attributes instead. But when you do need to specify a font name in Emacs on the Mac, use a standard X font name:
Section B.7. Wildcards are supported as they are on X.
Native Apple fonts in Mac Roman encoding has maker name apple and charset mac-roman. For example 12-point Monaco can be specified by the name -apple-monaco-*-12-*-mac-roman.
Native Apple Traditional Chinese, Simplified Chinese, Japanese, and Korean fonts have charsets big5-0, gb2312.1980-0, jisx0208.1983-sjis, and ksc5601.1989-0, respectively.
Single-byte fonts converted from GNU fonts in BDF format, which are not in the Mac Roman encoding, have foundry, family, and character sets encoded in the names of their font suitcases. E.g., the font suitcase ETL-Fixed-ISO8859-1 contains fonts which can be referred to by the name -ETL-fixed-*-iso8859-1.