M - Mnemosyne

 I was back in the dentist chair this morning.  An old filling was wearing out and the dentist was replacing it.  This dentist office is pretty laid back.  As he was prepping he was telling his assistant that he read in the local paper that a water main had broken in the city but that the paper reported "All was cleaned up before morning rush hour."  (The city's population is 3,500.)  The dentist smirked, "How much of a rush hour is there?"  The assistant handed him something.  "Hmmm." she mused,"If we have one I doubt it lasts a whole hour."  You try laughing when your mouth is wide open, full of dental instruments, and half of it is frozen w/ Novocain.

I only found a silent 'M' in words that begin w/ 'Mn'.  Checked out the Greek Mythology Family Tree poster I have pinned up on my bulletin board.  Yes, Mnemosyne - goddess of memory - was there among the Titans.  A yellow circle shows where she falls in that group.  Also included a better picture of her here.