168 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



has the same number of teeth as the true crocodile. Its 

 fourth mandibulary also fits into a notch in the upper jaw. 

 In these points it is related to the crocodilus genus. How- 

 ever, its upper teeth bite outside its lower ones, as in the 

 alligators and caimans, and it has a bony nasal septum 

 like the alligators. 



Alligators and Caimans have the fourth mandibulary 

 tooth fitting into a pit in the upper jaw, and their upper 

 teeth bite outside the lower ones. Alligators have a bom^ 

 nasal septum. The arrangement of the teeth leaves a 

 series of indentations on the upper and outer surfaces of 

 the lower jaw. Caimans have no bony nasal septum, and 

 their shields are articulated together as well as having 

 bony plates in the dorsal and ventral shields. It should 

 be mentioned that thin ossifications are said to be found 

 in the ventral shields of the Chinese and third species of 

 alligator. 



An interesting point in connection with crocodilian 

 teeth is the fart of the first mandibulary ones usually 

 piercing the promaxilla 1 and shewing superiorly. In a 

 tanned Caiman's skin (C. sclerops), measuring eight feet 

 in length, one of the fourth mandibular teeth had bitten 

 through its pit, leaving a mere bridge of bone and integu- 

 ment bridging across what was virtually a notch. 



The snout in the young gavial is proportionately 

 much longer than in the adult form. In a young, rough- 

 eyed or spectacled Caiman, the reverse is apparently the 

 case, as this particular specimen's snout has increased in 

 length. In studying a graduated series of C. niloticvs, 

 ranging in size from a foot up to thirty inches, I have 

 found the proportion of the snout's length increase with 

 growth.* 



* In specimens of about 12 or 15 inches in length the ratio the 

 length of snout bears to its basal width is about 1-2 : 1. The ratio 

 increases to 1-3 in specimens of 24 inches. 



