236 THE POPULAR SCIENCE MONTHLY 



ANT-HILL FOSSILS 



By Professor RICHARD SWANN LULL 



YALE UNIVERSITY 



LAST summer it was the writer's privilege to lead a small expedi- 

 tion from Yale to the fossil fields of the west in search for the 

 relics of bygone creatures to add to the already extensive collections 

 owned by the university. Our purpose was not solely that of collecting, 

 however, but to get data concerning the distribution in time of certain 

 of the ancient faunas, hoping thereby not only to increase the sum of 

 our knowledge, but to date more accurately some of the wealth of forms 

 collected by the pioneer expeditions which, under the leadership of 

 Professor Marsh, penetrated the unknown west in the early seventies. 



The work was partly in Nebraska exploring the Tertiary rocks for 

 the remains of warm-blooded mammals — horses, camels, rhinoceroses, 

 elephants, and their kindred — and partly in eastern Wyoming, where 

 one finds sediments of greater age containing the earthly inhabitants of 

 the closing years of the Age of Reptiles. The mammal collecting is an 

 old, old story, but the work in Wyoming had many novel features and 

 forms the theme of this brief essay. 



The Mesozoic rocks, those of the Age of Reptiles, are exposed with 

 their contained fossils in many places in this broad earth of ours, but 

 nowhere to a greater advantage than in the west, and this is particularly 

 true of the states of Wyoming, Colorado and Montana. One of the 

 counties of eastern Wyoming, formerly called Converse county, is 

 now divided into two portions, of which the westernmost retains its 

 ancient name, while the eastern part has been called Niobrara after the 

 long Nebraska river whose source lies here. The latter county includes 

 one of the most notable of Mesozoic localities, the beds lying on either 

 side of the confluent Lance and Lightning creeks. The former of these 

 is a tributary of the Cheyenne river, through which its waters flow into 

 the Missouri on their long journey to the Gulf. 



The strata here exposed belong to the ultimate phase of the Cre- 

 taceous period, marking the very close of the Reptilian age and possibly 

 its passage into the Age of Mammals. They cover an area of more 

 than sixty square miles, and, because of their geographical locality, have 

 received the name of Lance formation, though they have been called 

 variously Converse County beds and Ceratops beds, the latter name 

 having reference to the most characteristic fossils, the horned dinosaurs 

 or Ceratopsia, whose huge three-horned skulls are the most remarkable 



