Mick Jagger will test his comic chops later this month as host of the “Saturday Night Live” season finale. The Rolling Stones frontman has been a musical guest twice before on the long-running NBC show, and the network said Thursday he will perform musically on the May 19 finale. But he has never been host before, a job that usually requires participation in several skits. The Rolling Stones mark their 50th anniversary as a band this year, but have yet to announce any activities to commemorate the occasion. Jagger last year put out a disc as part of a group called SuperHeavy, which also included reggae singer Damian Marley and former Eurythmics founder Dave Stewart. … Energy businessman David H. Koch is donating $35 million to the Smithsonian’s National Museum of Natural History to build a new dinosaur hall on the National Mall, the museum complex announced Thursday. The donation by the executive vice president of Koch Industries Inc. of Wichita, Kan., is the single largest gift in the museum’s 102-year history. The Smithsonian Board of Regents voted to name the new hall in Koch’s honor. Koch, an engineer trained at MIT, is a billionaire who lives in New York City. He was the Libertarian Party’s vice presidential candidate in 1980 and has been a major donor to conservative political causes, as well as to educational, medical and cultural groups. Koch previously gave the Smithsonian $15 million in 2009 to build a new exhibit hall exploring human evolution over 6 million years. The museum’s Hall of Human Origins also was named in his honor. In 2006, he gave $20 million to the American Museum of Natural History in New York City to create the David H. Koch Dinosaur Wing. And in 2008, he gave a record $100 million to New York’s Lincoln Center to renovate the former New York State Theater.