454 CROCODILIA 



others in Colorado, were large-sized Crocodiles, some witli a skull 

 2 feet in length. The dermal armour consisted of a pair of 

 dorsal rows, a thoracic and an abdominal shield, composed as in 

 the Teleosauridae of six to eight longitudinal sutured rows. 



Fam. 7. Crocodilidae. — Beginning in the Upper Cretaceous 

 period of Europe and North America, many forms of Crocodiles, 

 Alligators, and Caimans existed in the Tertiary period in America, 

 Europe, and India ; persisting in Europe until the Plistocene. The 

 vertebrae are procoelous. The choanae are completely surrounded 

 by the pterygoids. The nasals reach the nasa^ groove, except 

 in Crocodilus cataphr actus. The orbits are larger than the small 

 supratemporal fossae, and always continuous superficially with 

 the lateral temporal fossae, the postfronto-jugal bridge not reach- 

 ing the surface. The dorsal armour consists of more than one 

 pair of longitudinal rows, while the ventral armour is much 

 reduced in thickness or absent. 



Diplocynodon. — Common in the Oligocene and Miocene of 

 Europe, e.g. D. hastingsiae. The skull resembles that of the 

 Alligators, but has a pair of lateral notches in the pre- 

 maxilla for the reception of the third, and sometimes also of the 

 fourth mandibular tooth. The ventral armour is still rather 

 strong. 



Crocodilus. — The fourth mandibular tooth fits, as a rule, into 

 a notch in the upper jaw. The other teeth are more or less 

 interlocked with those of the other jaw. The fifth upper tooth 

 is the largest. The nasal bones form the posterior border of the 

 nasal groove, but do not extend into it as a septum. The bony 

 scutes of the dorsal shield are keeled, and stand closely together, 

 being rarely united by suture ; and they form from four to six 

 principal rows. 



Crocodiles have occurred since the Upper Chalk in Europe ; 

 many species existed in the Tertiary epoch in Europe and North 

 America, decreasing in numbers in the Pliocene and disappearing 

 with the beginning of the Plistocene. About ten recent species 

 are known, and these have now a somewhat scattered distribu- 

 tion ; namely, three species in Africa, one of them extending into 

 Syria ; three in tropical America and the West Indian Islands ; 

 the rest in the Malay, Indian, and North Australian countries. 



0. palustris. — The " Mugger " of India. The premaxillo- 

 maxillary suture is transverse, as in the Alligators. The adults 



