Rachmaninov's Rhapsody on a Theme of Paganini, Op. 43

I listened to a lot of Rachmaninov to-day, including his Rhapsody on a Theme of Paganini, Op. 43.  I noticed that he includes "Dies Irae" in Variation X and Variation XXIV.

(notation found here)

If my counting is correct, this is measure 26 of Variation X.  This phrase also appears an octave higher two measures earlier, but this one was easier to take a screen clipping of.

In Variation XXIV, it appears at measure 39, again, if my counting is correct.  (I had to take two screen clippings to show the whole phrase.)  Here, he also slows it down in note values and changes the E to an Eb.