GEOLOGY IN NATIONAL MUSEUM MERRILL. 273 



At either side of the Basilosaurus skeleton are exhibited fine ex- 

 amples of the American mastodon (Mammut americanum) exhumed 

 from peat bogs in northern Indiana and southern Michigan. The 

 so-called Irish elk {Alee gigantea), from the peat bogs of Ireland, 

 with its wide-branching palmate horns, that have a spread of 8 feet, 

 9 inches, is a striking specimen of its kind. 



Passing to the large reptilia, the most conspicuous is a mounted 

 skeleton of the gigantic horned dinosaur (Triceratops) , a creature 

 with the largest head of any land animal the world has ever known. 

 This skeleton is 20 feet in length and 8 feet in height in front of the 

 hips, the skull being nearly one-third the total length of the animal. 

 In addition, this skull is further characterized by the development 

 of a great bony shield that overhangs the neck, and by two large 

 sharply pointed horns projecting forward from above the eyes with 

 a third smaller one developed on the nose. The three horns sug- 

 gested its name, Triceratops, meaning three-horned face. The re- 

 mains of this specimen, together Avith many others of its kind, are 

 from eastern Wyoming. While Triceratops represents the largest 

 and culminating group of its race, the Brachyceratops montanensis 

 is the smallest horned dinosaur yet described and one of the earliest, 

 geologically, of this peculiar group of reptiles. This skeleton, which 

 is a few inches less than six feet in length, has a skull that is only 

 22 inches long. Its diminutive size, as compared with the large 

 Triceratops, is clearly indicated in plate 6, figure 2. 



In addition to the two articulated skeletons mentioned above, the 

 Ceratopsia, as this group of horned dinosaurs is named, is repre- 

 sented by several fine skulls and numerous other portions of skele- 

 tons. The scientific importance of the collection is notable because of 

 the considerable number of type specimens, among which may be 

 mentioned Triceratops calicornis. T. obtusus, T. elatus, T. alticomis, 

 and Diceratops hatcheri. 



Against the north and south walls in the center of the main hall 

 are two dinosaur skeletons mounted in high relief. On the south side 

 is the large plant eating duck-billed Trachodon annectens, an animal 

 30 feet in length, that in life walked around largely on his strong- 

 hind limbs. This came from Wyoming also and was a contemporary 

 of the Triceratops previously mentioned. On the north side stands 

 a flesh eating Ceratosaurus nasicornis, a powerful but agile animal 

 seventeen feet in length and 5 feet high at the hips. In life the 

 creature subsisted on the flesh of other animals, as indicated by the 

 jaws with strong, sharp-pointed teeth that were well adapted to the 

 seizing of its prey and the subsequent tearing and rending of flesh. 

 One of its distinctive features is the presence on the nose of a single 

 well-developed horn. This animal is exceeded, however, in size by the 



