Though hardly landmarks of narrative or animation art, the first two Ice Ages were warm and goofy and appealing; John Leguizamo’s adorably sibilant Sid the Sloth remains a much-quoted guy in our household. But as with Shrek and countless other overextended studio franchises, the well has run bone-dry. Part Three sends woolly mammoths Manny (Ray Romano), a very pregnant Ellie (Queen Latifah), and the rest of their cobbled-together family of misfits to a lush land below the ice that’s fraught with dangers—like a burping purple plant that ingests foreigners—and teeming with the endlessly marketable dinosaurs so carelessly dispatched in the first movie. However spuriously gussied-up with 3D, this verdant underworld is a playground for animation geeks, but its narrative pull hovers around zero—unless you count the lame post-millennial jokes about helicopter parents and single dads doubling as single moms, and even those are nothing but an excuse to float a raft of cuddly prehistoric babies for audience tots and their elders to coo over. Even with the addition of an (obligatory Cockney) weasel (Simon Pegg) to steer the herd through the usual slalom ride of hot lava and hostile beasties, there’s no breathing life into a formula that ought to have bowed out gracefully while the going was good.