12 THE COLLECTION OF FOSSIL VERTEBRATES 



broad shallow valleys in the chalk and shale. In the dry climate 

 _. ,_ of the present day the sides of these valleys often are 

 ing and bare rock, carved by wind and the infrequent storm - 

 Collecting bursts of rain into the fantastic maze of cliffs and 

 of Fossils. ^|j-^(;|ij-ig caiions known as "bad-lands." Here and 

 there, projecting from an outstanding ledge or trailing in frag- 

 ments down some crumbling slope, a fossil bone may be seen by 

 the trained eye of the collector as he searches along the rock 

 exposures ; and quarrying in around the bone he is sometimes 

 rewarded by a skull, sometimes by a string of vertebrte, occa- 

 sionally by a whole skeleton, buried in the rock except for such 

 parts of it as have been weathered out and washed away. 



To excavate the fossil without damaging the brittle bones, 

 buried as they are in a weak and shattered mass of heavy shale 

 or chalk, is a slow and delicate operation, requiring special 

 methods and considerable care and skill. Then the specimen 

 must be packed, and sent in to the ]\Iuseum, where the rock is 

 removed and the specimen is prepared for exhibition. When the 

 bones are as much crushed and distorted as those represented in 

 the photograph (page lo) the matrix is removed from one side 

 only, and the specimen is thus placed on exhibition. 



Temporarily placed in the bottom of the case is a large Ple- 

 siosaur skeleton, only partly removed from the rock. This 

 Important specimen unfortunately lacks the skull. Beside the 

 Specimens lower Stairway is a Mosasaur skeleton, the finest speci- 

 ■ men of its kind ever found, and above it is a large fish 

 skeleton which was found in the same strata in western Kansas. 

 Beside the upper stairway are three skeletons of Ichthyosaurs, 

 another long extinct group of marine reptiles, of fish-like appear- 

 ance, paralleling the modern Whales among mammals. 



EAST WING. HALL NO. 406. FOSSIL MAMMALS. 



The ancestors of our modern quadrupeds are to be found in 

 the East Wing, No. 406, together with many extinct races more 

 Arrangement or less nearly related to them. All the fossil speci- 

 of the Fossil mens of each group of mammals are placed together 

 amma s. -^^ ^^^ alcove, where they have been arranged ac- 

 cording to their geological age. Thus all the fossil Horses, direct 



