152 WATER REPTILES OF THE PAST AND PRESENT 



Perhaps nowhere in the world are the fossil remains of marine 

 animals more abundantly and better preserved than in these 

 famous chalk deposits of Kansas. The exposures are of great 

 extent — hundreds of square miles — ^and the fossil treasures they 

 contain seem inexhaustible. Long-continued explorations by col- 

 lectors have brought to hght thousands of specimens of these 

 swimming lizards, some of them of extraordinary completeness 

 and perfect preservation, so complete and so perfect that there is 

 scarcely anything concerning the mosasaurs which one might hope 

 to learn from their fossil remains that has not been yielded up by 

 these many specimens. The complete structure and relations of 

 all parts of the skeleton, impressions of the bodies made in the soft 

 sediments before decomposition had occurred, the character of 

 their food, , the nature of the skin covering, and even some of the 

 color markings of the living animals have all been determined with ' 

 certainty. Not only from Kansas, but also from many other 

 parts of the world, have remains of these animals been discovered, 

 until now it may truthfully be said that no other group of extinct 

 reptiles is better represented by known fossil remains than the 

 mosasaurs. From England, Belgium, Russia, and France in 

 Europe; from New Jersey, Georgia, Alabama, Mississippi, Texas, 

 New Mexico, Colorado, Kansas, Nebraska, the Dakotas, Wyo- 

 ming, and other places in the United States; from New Zealand 

 and South America they have been obtained in greater or less 

 abundance and perfection. 



Their geological history is relatively brief, notwithstanding 

 their wide distribution over the earth in such great numbers and 

 diversity. The earhest are known from near the beginning of the 

 Upper Cretaceous of New Zealand, whence it is believed by some 

 that they migrated to other parts of the world, appearing in 

 North America some time later. They reached their culmination in 

 size, numbers, and variety very soon, and then disappeared forever 

 before the close of Cretaceous time. The largest complete speci- 

 men of a mosasaur known measures a httle more than thirty feet 

 in length, but incomplete skeletons of others indicate a maximum 

 length of about forty feet. The skulls of the largest species are 

 about five feet long. The smallest known adult skeletons are 



