1 192 



CLASS REPTILIA. 



isted, since it is most unlikely that the change from amphiccelous 

 to proccelous vertebrae took place precisely at the same time as the 

 pterygoids developed palatal plates. On the other hand there is an 

 equal prima facie probability that these two changes may have 

 occurred in the reverse order to that indicated above. 



B. Proccelian Series. — In this series the vertebrae, with the 

 exception of five, are proccelous ; the pterygoids develop palatal 

 plates to prolong the narial passage (fig. 1089) ; and all the 



eustachian canals are enclosed in 

 bone. The dorsal scutes are, more- 

 over, always arranged in more than 

 two longitudinal rows ; and when 

 there is a ventral buckler it is un- 

 divided, and invariably consists of 

 more than eight rows of imbricating 

 scutes, in which each scute is com- 

 posed of two separate pieces of bone. 

 The axis vertebra differs from that of 

 the Teleosauridce, in having no costal 

 articulations ; its rib having been 

 shifted forward on to the centrum of 

 the atlas, or odontoid process. 



Family Crocodilhle. — All the 

 sufficiently known members of this 

 series may be included in a single 

 family, which agrees with the Gonio- 

 pholididce in the free communication 

 of the infratemporal fossa with the 

 orbit, which is considerably larger 

 than the supratemporal fossae. This 

 family is first definitely known from 

 the Upper Cretaceous, and contin- 

 ues to the present day, being repre- 

 sented in the freshwaters of most 

 of the warmer regions of the globe. 

 If, however, the proccelous vertebrae 

 mentioned in the last series from the Greensand and Wealden 

 really indicate members of the present family, it will date from the 

 latter horizon. The form of the skull affords grounds for two sec- 

 tional divisions. 



The Longirostrine section is represented at the present day only 

 by the true Gharial (Garia/is) of the Ganges, and Schlegel's Gharial 

 of Borneo. The skull is produced into a long narrow rostrum (fig. 

 1 091), with the dental borders nearly straight; the nasals never 

 extend to the anterior nares, and are frequently separated from the 



Coec 



Fig. 1089. — Palatal aspect of the cranium 

 of Crocodilus. Reduced. Pmx, Premax- 

 illa ; M, maxilla ; PI, Palatine ; Ts, Trans- 

 verse ; Pt, Pterygoid ; Jg, Jugal ; Qj, 

 Quadratojugal ; Qu, Quadrate ; Ob, Basi- 

 occipital ; Cocc, Occipital condyle ; Orb, 

 Orbit ; Ch, Posterior nares. 



