Dear Brother
joseph lentz, I hope this helps with your question.
Act 1:26 And they gave forth their lots; and the lot fell upon
Matthias; and he
was numbered with the eleven apostles.
1 Cor 15:5 And that He (Jesus) was seen of Cephas, then of the twelve: (Note that Judas was no longer part of the twelve)
Note the following excerpt from a study of Acts at:
http://www.gracegod.com/Study Books/Acts of the Apostles.pdf
NOTE: The Grace and Glory Study books are in PDF format and can be read with the free
Adobe Reader
“Let Paul answer for himself. In I Corinthians 15, he is recounting the occasions on which Christ was seen and by whom, after His resurrection. He declares that "He was seen of Cephas, then of the twelve ... after that, He was seen of James, then of all the apostles. And LAST OF ALL, He was seen of me also, as of one born out of due time" (Verses 5-8). A careful study of the following citations shows that there were at least seven other apostles besides the 12, and that Paul was one of that group. (Acts 19:22 with II Corinthians 8:18, 23; I Thessalonians 1:1 and 2:6 with II Corinthians 1:19; Acts 14:14; I Corinthians
4:6, 9; Philippians 2:25) The word "messenger" in II Corinthians 8:23 and Philippians 2:25 is "apostle" in the original Greek text. It is translated apostle in the Revised Version. Paul was the chief apostle of another group, the Church, for another and distinct purpose, even as Peter was the leader of the 12 apostles of the Lamb.”