Another Sentence

Hi guys, here's a sentence that actually would've appeared as part of a Linguistics course description in next semester's catalog, except I caught it and fixed it up on the sly (shhh!). My eventual solution was to cut it entirely, but here it is:

"Of the other varieties, Caviteno (and perhaps Ternateno), spoken on Luzon south of Manila, in the areas of Cavite and Ternate, still have some life, although they are certainly endangered."

After I finished tripping over all commas, my first question was, “The other varieties of what?” Languages? Dialects? Jargons? It's not stated here, and I wasn't able to glean it by context from surrounding sentences. “Spoken on Luzon south of Manila” needs a comma in the middle of it, since I'm pretty sure that “south of Manila” is in apposition to “Luzon.” Also, the way the sentence is written, I think “have” and “they are” should really be “has” and “it is.” I'm pretty sure that “Ternateno,” being parenthetical, doesn't actually count as a compound subject; the subject is the singular “Caviteno,” as opposed to the plural “Caviteno and Ternateno.” I can't actually find a rule about parenthetical stuffs to back me up here, so if anyone knows, please post a comment!

If I had to rewrite it, it would look like this:

Of the other dialects, Caviteno and (perhaps) Ternateno—both spoken on Luzon, south of Manila, in Cavite and Ternate respectively—still have some life, although they are certainly endangered.

I tried to keep the changes minimal, but I hope it reads a bit more smoothly now.