Weird behavior with find command when tarring files

find . type f -mmin +239 | xargs tar -cvf /tmp/test.tar

The command tars up files and seems to finish fine. However, when I untar and count the number of files against the count of files that should have been captured (find . type f -mmin +239 | xargs ls -l | wc -l) there is a huge difference and the files captured by tar were way less than the file listed for the same time.

This is a strange behavior. What am I doing wrong (I am sure I am doing something wrong)?

Thanks,
Amir