SEPTEMBER 16--Here's the mug shot O.J. Simpson posed for today following his arrest for the alleged armed robbery of a memorabilia dealer in a Las Vegas hotel room. Simpson, 60, was booked into the Clark County Detention Center after he was taken into custody this morning by Las Vegas Metropolitan Police Department officers. According to investigators, Simpson and several cohorts burst into a room at the Palace Station hotel Thursday evening and confiscated collectibles that Simpson claims were stolen from him (the items were being offered for sale by a dealer with whom Simpson has had prior business dealings). Simpson, who is facing six felony charges, is the second person arrested for the alleged memorabilia heist. Walter Alexander, a 46-year-old Arizona man, was nabbed last night on armed robbery, assault with a deadly weapon, and conspiracy raps. Two firearms were seized during search warrants executed following the arrest of Alexander, whose booking photo can be found here. The weapons, cops contend, were the ones used during the hotel heist. Simpson last posed for a mug shot in June 1994 after he was arrested for killing his ex-wife and her male companion. A Los Angeles jury later acquitted him of murder charges. (2 pages)