i6 



CROCODILES. 



halves of the lower jaw are united in front by a very short bony union. The 

 stout teeth vary considerably in size in different parts of the jaws ; the third and 

 ninth in the upper jaw, the fourth, and frequently also the first and eleventh, in 

 the lower, being generally much larger than the others. In these features caimans 

 and alligators resemble many of the true crocodiles ; from which they are distin- 

 guished by the circumstance that, as a rule, both the first and the fourth tooth on 

 each side of the lower jaw are received into pits in the upper jaw, so as to be 

 invisible externally when the mouth is closed ; while the upper teeth bite on the 

 outer side of the lower ones. Moreover, the number of teeth varies from seventeen 



SPECTACLED CAIMAN (fj nat. size). 



to twenty on each side of the upper jaw, and from seventeen to twenty-two in 

 the lower jaw. Then, again, both these groups are characterised by the very small 

 size of the upper temporal fossae on the top of the skull, or those marked T in the 

 figure on p. 13 ; these fossae being in some cases completely obliterated. Caimans 

 are specially distinguished by the aperture of the nostrils not being divided in two 

 by the nasal bones, by the presence of a strongly developed bony armour on the 

 inferior surface of the body, and by the bony plates on the upper surface being 

 articulated together. 



Caimans, or jacares, as they are called by the natives of Brazil, are restricted 

 to Central and South America, where they are represented by five species. Of 

 these, the largest, and at the same time the best known, is the black or great 



