What's the difference between "e.g." and "ex."? [closed]

E.g. is short for exempli gratia, and is in common use to introduce an example within a sentence.

Submit a sample of academic writing, e.g., a dissertation chapter.

However, some authors use ex. or ex: (short for "example") for the same purpose, and this form is listed in some authorities like the Wiktionary.

Submit a sample of academic writing, ex: a dissertation chapter.

I know they both roughly mean "example", but which one should I use, and when? Are there connotations associated with one or the other?

This question has been asked elsewhere, and this very answer comes up when you ask Google about the difference. It would be good to get an EL&U answer for it.

E.g. is short for exempli gratia and stands for "for example". Ex., if used to mean the same, is incorrect. Mostly ex. is used as short for exercise and not "for example".

"Ex." is not very common, but it may be used to refer to a cited example, eg "See ex. 3".

"E.g." is much more common, and is used to introduce an example, or series of examples. In speech, it is usually replaced by "for example".