Note 14 at 1 Cor. 15:7: There is no individual appearance of the resurrected Jesus to James recorded in the Gospels or in the book of Acts. In fact, it is not certain which James, of the five mentioned in scripture, this is referring to (see note 3 at Mk. 1:19, p. 115). Most scholars believe this was the James who was the half brother of Jesus (see note 2 at Jn. 2:12, p. 88) and who became the head of the Jerusalem church. This could be a reference to a special appearance of Jesus after His resurrection to His half brother, who didn't believe in Him before the resurrection (Jn. 7:5).

Note 15 at 1 Cor. 15:7: The twelve apostles had already been mentioned, now he says Jesus appeared to all the apostles. This makes it very clear that there were more than just twelve apostles.

James, the half brother of Jesus, was called an apostle (Gal. 1:19). Just two sentences later, Paul calls himself an apostle. Barnabas was also called an apostle (Acts 14:14).

Some people have believed that for an individual to be an apostle, he had to be a witness of Jesus' earthly ministry, which leads them to believe there are no apostles today. This is based on Peter's statement in Acts 1:21-22 when they were selecting a replacement for Judas. However, there were hundreds of thousands who saw Jesus during His earthly ministry. Did that make them apostles? Certainly not. There was more to being an apostle that just seeing Jesus during His physical ministry here on Earth.

When Paul was defending his apostleship to the Corinthians, in 2 Corinthians 12:12, he put more emphasis on the miraculous power of the Holy Spirit as evidence of apostleship. In scripture, apostles are the highest authority in the church, with what many today would call a missionary calling (see note 18 at 1 Cor. 12:28, p. 935). These individuals still exist today.

Ephesians 4:11 lists the apostle as one of the ministry gifts given unto the church. In verse 13 of that same chapter, Paul makes it very clear that this gift of the apostle was given "Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ." That certainly hasn't happened yet, so we can be assured that God is still gifting people with the calling of an apostle.