2372 CROCODILES, DINOSAURS, AND FLYING DRAGONS 



and the nasal bones extend forward to the aperture of the nostrils,* while the two 

 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 alliga- 

 tors resemble many of the true crocodiles; from which they are distinguished 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 



SPECTACLED CAIMAN. 

 (One-fifteenth natural size. ) 



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 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 characterized 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. 2369; these 

 fossae being in some cases completely obliterated. Caimans are specially distin- 

 guished by the aperture of the nostrils not being divided in two by the nasal 



*This is shown in the figure on p. 2358, where the nasals are the paired bones on the upper aspect of the 

 skull, of which the narrow points just project into the cavity of the nostrils. 



