INTRODUCTION 7 



stones" reveals something of the food habits, and even of the struc- 

 ture of the aHmentary canal, etc. 



All this information is gained slowly, often very slowly, and with 

 much labor and pains. Rarely or never is it the case that all 

 the information obtainable concerning any one kind of an extinct 

 animal is furnished by a single specimen. Skeletons are very sel- 

 dom, perhaps never, found quite complete, with all their parts in 

 their natural positions; and the nature of the matrix inclosing them 

 usually prevents a study of all parts of any specimen. If a newly 

 discovered fossil is widely dilTcrent from the corresponding parts 

 of any creature previously known, whether living or extinct, we 

 cannot infer very much from a few bones as to what the remainder 

 of the skeleton is like. Such inferences or guesses in the past have 

 often resulted in grievous error, and self-respecting paleontologists 

 are now very reluctant to speculate much concerning extinct 

 animals from fragments of a skeleton, no matter what those frag- 

 ments or bones may be; future discoveries are sure to reveal errors. 

 It is, therefore, only by the accumulation of much material, and 

 by the careful study and comparison of all known related animals, 

 that reHable conclusions can be reached. Often it requires scores 

 of specimens to determine the exact structure of a single kind of 

 animal, and, as the collection and preparation of fossil skeletons 

 are tedious and expensive, our knowledge sometimes increases 

 very slowly. In recent years, however, there have been many more 

 students of extinct backboned animals than formerly, and there 

 are now many museums and universities which spend annually 

 large sums of money in the collection and preparation of such fos- 

 sils. This greater activity of the last twenty years is bringing to 

 light many new and strange forms, as well as completing our 

 knowledge of those previously imperfectly known. 



It is commonly, but erroneously, believed that the bones of 

 extinct animals are usually found in excavations made for the pur- 

 pose. It is true that not a few specimens of fossils have been 

 discovered in excavations made for other purposes, such as 

 railway cuttings, quarries, wells, etc., but if no others were found 

 our knowledge of the animals of the past would be very meager 

 indeed. Fossils are, for the most part, found by deHberate search 



