REPORT OP THE SECRETARY 7 



period of erosion that cut out the Rocky Mountain Trench. On the 

 eastern side of this valley, the Mons formation is more than 3,800 

 feet in thiclmess in the Beaverfoot-Brisco-Stanford Range, and con- 

 tains four well-developed fossil faunas Avhich show it to lie between 

 the Upper Cambrian and the Ordovician systems of this and other 

 parts of the continent. Near the head of the Sinclair Canyon there 

 was discovered a great development of the LoAver Ordovician, and 

 at several localities cliffs of massive Upper Cambrian limestones 

 were recognized beneath the Mons formation. 



This whole region is ideal for geological field work, as the numer- 

 ous canyons and ridges expose many of the formations from base to 

 summit. On the whole, the season was a successful one for its geo- 

 logical results. 



EXPEDITION TO DINOSAUR NATIONAL MONUMENT, UTAH 



In May, 1923, Mr. C. W. Gilmore, curator of vertebrate paleon- 

 tology. National Museum, was detailed to take charge of an expedi- 

 tion to the Dinosaur National Monument in northeastern Utah for 

 the purpose of securing for exhibition in the Museum a mountable 

 skeleton of the large sauropodous dinosaur, Diplodocus. The fossil 

 deposit in this region was discovered in 1909 by Mr. Earl Douglass, 

 and has been worked continuously since that time by the Carnegie 

 Museum of Pittsburgh. By 1922, the Carnegie Museum had secured 

 sufficient material for their purposes, and the Institution was notified 

 of their intention to cease operations, leaving uncovered two partially 

 articulated specimens of Di'plodocus^ a mountable skeleton of which 

 has long been desired by the National Museum. Mr. Gilmore ar- 

 rived at the fossil quarry on May 15, and a preliminary survey showed 

 that one of the two skeletons would form the basis of a mountable 

 specimen while the preserved parts of the other would serve ad- 

 mirably to replace the missing bones of the first. Regular work in 

 the quarry began on May 24 and continued until August 8. "Mr. 

 Gilmore employed three men with experience in this field, and was 

 assisted after June 5 by Mr. Norman H. Boss, of the Museum's 

 paleontological force. Regarding the difficulties involved, Mr. Gil- 

 more says : 



The work of quarrying these often fragile bones from the ledge of rock 

 without doing irreparable damage is a slow and tedious operation, involving 

 the skill of both the stone cutter and the miner. Further difficulty is encountered 

 in handling by primitive methods the immense blocks of rock inclosing the 

 bones, with the subsequent arduous work of boxing and transportation. The 

 largest block quarried, containing the sacrum with attached hip bones, weighed 

 nearly 6,000 pounds when ready for shipment. The transportation of the boxes 

 to the railroad involved a haul by teams of 150 miles across country and over 

 a range of mountains 9,100 feet above sea level. However, 34 large boxes hav- 

 ing a combined weight of over 25 tons were safely transported. 



