Did you know that there was no 3rd or 4th Nephi in the first edition Book of Mormon?

There were, however, the following books:

First Book of Nephi
Second Book of Nephi 
The Book of Nephi: The Son of Nephi, Which was the Son of Helaman
The Book of Nephi: Which is the Son of Nephi, One of the Disciples of Jesus Christ.

In 1879, at the recommendation of Orson Pratt, 3rd and 4th Nephi were added to the chapter titles for clarification.  If you look at a modern printing you will see that the the complete titles are now as follows:

THIRD NEPHI
THE BOOK OF NEPHI
The Son of Nephi, Who Was the Son of Helaman

and

FOURTH NEPHI
THE BOOK OF NEPHI
Who is the Son of Nephi--One of the Disciples of Jesus Christ

The 1879 edition is also the first time that the chapters are divided into verses.