Bergmann's Martian Colony, Bk 8 — George G. Pinneo

This hard SF novel continues Bergmann's team's establishment of an interspecies colony at Candor Cliffs above the new sea in Valles Marineris in the Martian Highlands on a terraformed Mars. They are stunned by finding an indigenous nautili race and are challenged to learn a new way of communicating with sapients.