What is the main setting in The Land That Time Forgot?

All three novellas are set in Caspak, a land where evolution occurs at a rapid pace. There is a large sea in the middle of Caspak, and the evolutionary chain works its way north along both the east and west sides. At the southern end of this interior sea are primitive creatures, while at the northern are Caspak's most advanced forms of life: human beings called "Galu" and hideous winged creatures called "Wieroo." These two species represent alternative courses of civilization and are mutually hostile.