On occasion Scripture does use the term "apostle" of those beyond just the twelve (see Acts 14:14). However, in Galatians 1:19 there may be another answer. Galatians 1:18 had just referred to Paul seeing Peter. In the original language the first words of the 1:19 are heteron de tōn apostolōn ouk eidon (literally, "But another of the Apostles I did not see"). The question rests on how to understand the next phrase. The words which most translations render "except" are the Greek words ei mē. This literally means "if not." The sense of "except" is usually inferred in saying "if not," but it does not necessarily mean that James is being counted as "another of the Apostles." Paul may simply be listing James, the Lord's brother as one of the notable figures he saw in Jerusalem. Acts 15:6-13 seems to include James among the elders in Jerusalem, and one of some prominence. This may be all that Galatians 1:19 is addressing.
Kyle Pope, July 2010