66 REPTILES OF THE WORLD 



As to the Chinese AUigator — it is the only crocodilian 

 found in the Yang-tse-Kiang River. The South 

 American Caimans have been described as belonging 

 to the "alligator group." All appeal to the two species 

 of alligator in internal (osteological) characters; yet 

 externally some look like the crocodiles, as they have a 

 pointed snout; others have a typical blunt, "alligator- 

 like" snout. This is a bird's-ej'e view of the whole 

 controversy. The alleged "striking difference in 

 structure of the teeth" will later be discussed in relation 

 to the respective species. 



Let us return directlj^ to the structure. On the chin 

 of all crocodilians is a pair of glands capable of being 

 literally turned wrong-side-out in expelling their con- 

 tents. They contain a strong-smelling, musky secre- 

 tion undoubtedly employed by the sexes in determining 

 each other's whereabouts during the breeding season. 



Except on the back, crocodilians are covered with 

 tough, leathery plates or shields, oblong on the abdomen 

 and rounded on the sides ; it is this part of the hide that 

 is commercially valuable. On the back and top of the 

 neck is an armor of large, close-set bony plates, attached 

 to a tough, leathery skin. Most of these plates are 

 coarsely keeled ; they are arranged in regular rows ; from 

 a technical point of view they compose the dorsal sheet 

 and are useful in the determination of species, as their 

 arrangement varies. 



One important character of the internal structure 

 should be noted. The development of the heart and 

 vascular system is the most perfect among all reptiles. 



General Habits: Crocodilians live in immediate 

 proximity to fair-sized bodies of water. Crawling out 

 on the banks to bask, they rush for the water when dis- 

 turbed, diving to the bottom. A common habit is to 



