86 THE AM ERICA X MISEIM JOIKXAL 



age outlet to the nortli into the Missouri River was formed. Theu condi- 

 tions changed, tlie process (jf dej)osition ceased, and that of erosion l)egan 

 and has continued to the present time. To-day the liig Horn Basin is 

 4,000 feet above sea level in its lowest parts, it is arid, in fact almost t)arren 

 except along the few water courses which lead down from the mountains, 

 and the erosion has remo\ed the greater part of the original 2,000 feet of 

 sandstone and clay. A few high, flat-to])pc(l luiltcs, left hy the erosion, 

 indicate the level of the Basin at tlie time when the erosion began, but for 

 the most part the formation has been worn down nearly to its base, and the 

 country ])resents great areas of low, rounded knolls and sharp, steep ridges 

 comprised chiefly of gray and rvi\ hard, brittle clays with occasional layers 

 of sandstone, and often absolutely bare of any vegetation. Such areas are 

 known to the geologist as "bad lands," and it is here that the fossil collec- 

 tor makes his search for the petrified remains of these ancient animals. 

 As the hills are slowly worn away by the heavy spring rains or an occasional 

 cloud-burst in summer, the bones which have l)een entombed for so long can 

 be tletected by the trained eye of the prospector. Often it is merely a 

 worthless fragment of bone, sometimes a fragment of jaw or a skull, and 

 in rare cases a nearly complete skeleton sucli as the present one. In such 

 instances it is probable that the ])ody of the animal became buried soon 

 after its death, before the bones could be scattered by carrion eaters or l)y 

 the action of water or otlier agents. 



The present skeleton was found by Mr. William Stein, who has l)een 

 employed as cook and teamster of the Wyoming expeditions for several 

 seasons and who spends his spare time in searching the l)ad lands, with 

 the rest of the party. The finding of fossils is largely a matter of keen 

 eyesight, of a certain amount of training in knowing what to look for, and 

 of ability to spend long days walking or slowly riding through the broiling 

 heat of the bad lands. It was the bleached fragments of the bones of the 

 hind legs which attracted the attention of the collector as they lay on the 

 sloping surface of a knoll. These surface fragments were carefully gathered 

 up, and a little careful prospecting showed the hip and backl)one of the ani- 

 mal extending into the solid clay of which the knoll is comijosed. By remov- 

 ing the overlying rock the whole ui)per part of the skeleton was exposed as 

 it lay on its side in a horizontal jiosition. Instead of removing the bones 

 one by one from the rock, the whole skeleton was taken out, with such of 

 the encasing rock as was lu'cessary, the entire mass being bound uj), as is 

 usual in collecting such specimens, in heavy bandages of l)vu-lap and paste. 



In the laboratory the bandages will be removed, and the slow, rather 

 tedious task of removing the small and extremely fragile bones froin the 

 rock will begin. It took three days to excavate the specimen in the field, 



