2o8 THE OSTEOLOGY OF THE REPTILES 



The most primitive reptiles that we know had no less than thirty- 

 seven pairs and four single bones in the skull. The crocodiles have 

 but twenty-four pairs and six unpaired bones in the adult; the 

 turtles have twenty-two or twenty-three pairs and five or six un- 

 paired bones; the lizards have at the most twenty-nine pairs and 

 five single bones. But not all are the same. The crocodiles have 

 three or four pairs that have been lost in the turtles; the turtles, one 

 pair that is fused in the crocodiles; the lizards, several bones lost or 

 fused in the turtles, and so on. All reptiles since Triassic times have 

 lost four bones in the pectoral girdle, and all have lost some bones of 

 the feet. The persistence or loss of bones furnishes many certain 

 evidences of relationships and descent. Each order must have de- 

 scended from ancestors that had the persistent bones; they could by 

 no possibility have regained them when once lost. 



The relative importance of all such characters in classification is, 

 however, largely a matter of the classifier's personal opinion. No 

 two persons see them from the same viewpoint and consequently 

 no two persons whose opinions deserve consideration ever wholly 

 agree as to the value of characters in classification. It is only in the 

 gradual crystallization of opinions that stability finally results, and 

 this crystallization is never complete. So long as science endures, 

 new facts will be discovered to influence our opinions. Any system 

 of classification, then, merely represents the present state of our 

 knowledge and the consensus of the opinions of those best qualified 

 to decide as to their value, more or less influenced by the classifier's 

 individual opinions. No classification will ever be perfect, for per- 

 fection postulates complete knowledge. Fortunately, however, the 

 increase of knowledge affects less and less the major principles, and 

 more and more subordinate details. 



