Well, little brats, you'd better start reading!
Sorry Legate, didn't pay enough attention I guess.
A cave troll...it's hard to compare him to anything else as we know so little.
Actually, after thinking about this a bit I realised that they aren't even necessarily a different type of troll at all. The three are enver specifically identified as Stone-trolls, only later Tolkien mentions in the Appendix that the Stone-trolls spoke the Common Speech. Thus it is plausible that this name only derives from the fact they turned to stone and that they were in fact Hill -trolls, like those that had slain Arador, Aragorn's grandfather, in the Ettenmoors.
I know this is not exactly on topic, just thought I might bring that into discussion, as I guess it's up to each of us to decide for himself if what is said in The Hobbit really fits with the rest of the works or not.