Speak with Mura Runetotem in the Sepulcher.
My clanmate, Mura Runetotem, traveled to Silverpine so that she might aid our undead allies. Silverpine is an ailing forest, a dying forest, and it was Mura's hope to bring it new life. Perhaps the strange life found here in the Barrens can help her work in Silverpine.
Take a sample of the shells you gathered, and bring it to Mura in Silverpine. She is staying at the Sepulcher. With luck, studying the shell will give her the insight she needs to heal that dying place.