Uh, you must be looking in a different edition. :o
–Cliffy
Always use the final comma in a series. It adds clarity, and is never wrong. (The basic position of the Chicago Manual of Style.)
Eschewing the comma was simply a fashion for a time.
I personally prefer consistent use of the serial comma, since occasionally it will avoid confusion, and its absence has no special justification. But I won’t cvonsider a consistent omission of the final comma a solecism.
However, any abbreviated word requires a period to signal the abbreviation. (This does not apply to portmanteau terms, initials of phrases used as words, and neologisms derived from such initials-of-phrases. So al. requires a period.
I also greatly prefer italicizing any formal-writing Latin locution used in English which has not come to be an accepted part of spoken English (Ibid., ceteris paribus, but etc., since people do use “et cetera,” even in relatively colloquial speaking, after providing examples to indicate their list is not exhaustive).