Lykins is the name given by Fenneman, in his bulletin on the geology of the Boulder district, to the upper portion of the "Red Beds" in the Front Range of eastern Colorado. The age of this formation has never been settled. It has been assigned to various ages from the Gpper Carboniferous to the Triassic, but is commonly spoken of as Triassic. This is due primarily to the almost total lack of fossil evidence. Up to the summer of 1910 there had been no well-autl.Jentieated report of fossils from this formation afong the entire range. In the summer of 1910 the Colorado Geological Survey sent out the writer and Mr. David L. C'urtis to examine the formation, with special reference to the determination of its age. The last direction from the state geologist was: "Bring back fossils from the Lykins formation." During the summer and fall we followed, with considerable care, the foothills from the, Wyoming line down to the New Mexico line, keeping as close to the outcrop of the Lykins as possible. In this work it was found necessary to study, to a greater or less extent, the underlying Lyons, Fountain and other Upper Carboniferous formations, and the overlying Morrison or Jurassic formations. That is, we had to keep. in touch with practically all the sedimentary formations from the pre-Cambrian to the Cretaceous. The topographic sheets of the United States Geological Survey were used for the geographical work.