Hollywood is not only mourning for the lost victims of last Tuesday's attacks, but there is widespread grief over the passing of two giants in the entertainment field, movie mogul Samuel Z. Arkoff and TV pioneer and longtime "Tonight" show producer, Fred De Cordova. Arkoff, 83, died Sunday of natural causes. De Cordova, 90, died Saturday at the Motion Picture and Television Fund Hospital in suburban Woodland Hills. A quintessential cigar-chomping producer, Arkoff, an Iowa-born lawyer, with his partner James H. Nicholson, launched their American-International Pictures in 1954 after securing a $3,000 bank loan. The kings of low-budget teen movies, Arkoff and Nicholson's output included such '50s drive-in classics as "I Was a Teenage Werewolf" (starring a very young Michael Landon) and "Beach Blanket Bingo" (with former Disney star Annette Funicello). De Cordova's movie credits actually included his direction of the much-lampooned Ronald Reagan comedy "Bedtime for Bonzo," though he was best known for his TV work, from directing "The George Burns and Gracie Allen Show" in the early '50s to producing - and sometimes appearing on, when the host dragged him reluctantly in front of the camera -- "The Tonight Show Starring Johnny Carson."