Indigo Girls [ tickets ] Amy Ray and Emily Saliers, who recently announced plans to head out on the their fourth annual Honor the Earth tour, have added 11 new dates to that tour. An additional date has also been added to the duo’s subsequent college tour.

Ray and Saliers will kick off this year’s Honor the Earth tour in Billings, Mt., on Sept. 30. Fourteen stops throughout the West and Midwest will follow in October, with a final date set for Oct. 19 on the Menominee Reservation in Wisconsin.

David Crosby [ tickets ], Bonnie Rait, Joan Baez [ tickets ], Jackson Browne, Indigenous [ tickets ] and a number of other acts are scheduled to perform with Indigo Girls on varying dates throughout the tour. The tour itinerary indicates that Saliers will perform without Ray at the tour’s Oct. 3 stop in Bozeman, Mt.

Proceeds from the tour will benefit Honor the Earth, an organization that raises funds for and awareness of Native American issues, according to tour organizers.

Following the Honor the Earth tour, Ray and Saliers have four college dates and a festival appearance lined up, beginning with an Oct. 20 show at Earlham College in Richmond, Ind. The last confirmed date on the Girls’ itinerary is an Oct. 28 stop at the Earth Challenge Benefit concert in Atlanta.

“Indigo Girls: A Retrospective,” a compilation featuring 14 of the duo’s previously released tracks and two new songs, is set for release on Oct. 3.

In addition to the two new songs on the forthcoming disc, a new track entitled “Point Hope F.O.I.A.” will be offered over the Internet as a paid download, with proceeds benefiting the Honor the Earth Foundation, according to Epic. A release date for the track and details on where to obtain it on the Internet were not available at press time.