I am currently reading Donna Tartt’s The Goldfinch, for which she won the 2014 Pulitzer Prize for Literature. I am into only a few chapters of this 700+ page book and enjoying it greatly. However, one sentence stopped me short. In a description of a living room, Tartt includes the following items:
“…silk-shaded lamps burning low, big dark paintings of naval battles and drapes drawn against the sun.”
Without a comma after “battles,” it sounds as if some of the painting were of those drapes. Usually, when items are in a series of three or more, that last comma (known as the Oxford or serial comma) can be omitted. I prefer not to use it: my motto is, “When in doubt, leave it out.” But at times it is needed for clarity. Logic may tell you some of the paintings were not of drapes, but this is an instance where a comma was called for.
Here’s a link to a short video about the Oxford comma: http://www.wimp.com/oxfordcomma/