CBS has apparently found a way to keep a lid on Captain Kangaroo. Robert Keeshan, who played the venerable children's host on the network for 30 years, until the lust for revenues forced him out, resurfaces on the air this morning as host of the new "CBS Storybreak" series, an anthology of animated book adaptations. The premiere, "The Great Ringtail Garbage Caper," at 11 on Channel 9, is based on a kiddy tome by Timothy Foote.

Keeshan has been occasionally outspoken on the sorry state of children's programming on network TV. His criticisms naturally touch upon the cancellation of his own program to make way for "The CBS Morning News," which hasn't been getting much better ratings, for all the fuss, than the Captain did. Installing him in the role of host for this show may be a network device for placating him. But it is an insulting role and Keeshan deserves better.

"Caper," adapted by Mark Evanier, looks like nearly every other tacky Saturday morning cartoon, even if it does, happily, lack mountain-smashing superheroes and boisterous monsters. The story concerns a pack of raccoons who are frustrated in their garbage raids by a new city sanitation truck under the supervision of workers Nip and Tuck, ha ha. Very edifying. Eventually they hijack the truck and gorge on trash.

The animation, credited to Hanna-Barbera's Australian studios, is drab, and the film has all the zip and dash of mononucleosis. Yet it's all safely innocuous and self-congratulatorily nice, and some goody-goody outfit will probably give "Storybreak" an award on the grounds that what would normally occupy its time slot would be worse and louder. As victories go, they don't get much littler than "Storybreak."