Vigil Office Confusion

I have been confused regarding the Vigil Office - as I finally discovered after Lauds today: I should have said Lauds II (whose first psalm is Ps 50) rather than Lauds I as usual. While there would be no obligation to do so in any case, I read the omitted parts later. My having to read the Vulgate psalms from Tome I of the Breviary, and the rest from Tome II, is probably to blame for this stuff-up; my Breviaries are mismatched, since Tome II has the horrible neo-Ciceronian psalm version in it, which I avoid by juggling the two volumes.