Abstract
Similarities of middle anld upper Paleozoic deposits of the Ellsworth fountains with those of the Pensacola, Horlick, and other Transtarctic mountains indicate that all these ranges may have had a related geologic history. A native explanation is now suggested which involves sea-floor spreading atnd anslocationi of the Ellsworth crutstal block from its originilal location adjacent to the East Antarctic Shield. Accordingly, the islands of West Antarctica may differ it origin and the Transantarctic Mountains of East Antarctica may represent one margin of an ancient rift.