6 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 81 



sixth mentioned above, and three distal ones displaced at the end. 

 The thoracic ribs of the lower or left side, except the first, were all 

 present and articulated with their respective vertebrae; those of the 

 upper or right side, except one found out of position, were all mis- 

 sing. The left hind leg and foot remained articulated but stretched 

 out in a sprawling position, as shown in Plate 4. The pubes, ischia, 

 bones of the pectoral girdle, and fore-limb bones were found to the 

 east of the main portion of the skeleton. The detailed list of the 

 skeletal parts found is as follows: 10 dorsal vertebrae; 5 sacral 

 vertebrae; 32 caudal vertebrae; 9 ribs (left), 1 (right); both ilia; 

 pubes and ischia; right scapula and coracoid; both humeri; both 

 ulnae ; one radius ; left hind leg and foot complete ; 18 chevron bones. 



In the accompanying diagram (fig. 1) made at the time of collect- 

 ing the specimen the bones of the skeleton are represented in the 

 position in which they were found embedded in the sandstone. 



The destructive work of wind, water, and frost in breaking down 

 fossil bones exposed to their action is well illustrated by certain 

 elements of this skeleton. 



Collectors from the Carnegie Museum had partially worked out 

 the skeleton from the conglomeratic sandstone in which it was 

 embedded, as shown in Plate 4. The bones thus uncovered remained 

 exposed to the action of the elements for nearly two years before 

 recovery, and in that time many of them were considerably damaged. 

 When first uncovered the preservation was almost perfect and the 

 bones were dark colored, but with exposure they whitened and 

 became much checked and broken, in several instances considerable 

 parts being lost. While some of the missing portions may perhaps 

 be attributed to vandalism, much of the loss is directly due to erosive 

 disintegration, that is, breaking up into such small particles made 

 it no longer possible to preserve the parts affected. On the other 

 hand, undisturbed bones were found to be dark in color and per- 

 fectly preserved. This is an interesting example of the rapidity 

 of the disintegration of fully mineralized bones when exposed to 

 the elements. 



The vertebrate fauna of the Dinosaur National Monument as 

 known at the present time is as follows: 



Dinosauria : 

 Saurischia : 



Apatosaurus louisae Holland. 



Barosaurus sp. 



Camarasaurus lentus (Marsh). 



Diplodocus sp. 



Pleurocoelus sp, 



JJititasaurus douglassi Holland. 



Antrodemus (Allosaurus) sp. 



