222 REPTILIA 



CL.\Jss m 



jaw equally enlarged, and either both received into pits of the upper jaw, or 

 the fourth passing into a marginal notch between the maxillae and premaxillae. 

 Dermal armour strongly developed. Abundant in Upper Eocene. (31igocene 

 and Miocene of England, France, and Germany. 



Bottosaurus, Agassiz. Imperfectly known, but with alligator-like dentition. 

 Upper Cretaceous ; New Jersey, Colorado, and Montana. 



Alligator, Cuvier. Eecent ; North America and China. Caiman, Spix ; 

 Jacare, Gray. Central and South America. 



Family 4. Crocodilidae. 



Skull anteriorly compressed. Orbits larger than supratemporal vacuities, confluent 

 with the lateral temporal fossae. Teeih irregulär, eighteen or nineteen in the upper, 

 and fifteen in lower jaw on each side, the two series mutually interlocking. Anterior 

 tooth in lower jaw received into a pit, and fourth tooth fitting into a marginal notch (m' 

 pit). Suture between maxillae and premaxillae on the palate transverse or concave in 

 front. Dorsal armour comprising more than two rows of scutes lying free in the 

 integument ; ventral armour wanting. 



Crocodilian remains occur extensively in the fresh-water Upper Cretaceous 

 and Tertiaries of Europe and North America, and in the Pliocene of India. 

 Recent species are distributed in tropical Africa, East India, New Guinea, 

 South America, and Cuba. The typical genus Crocodilus, Laurill. (Figs. 320, 

 322, 323), is divided into a number of sub-genera, and is met with in the fossil 

 State as early as the Upper Cretaceous of Europe. 



Range and Distribution of the Crocodilia. 



The earliest remains referred to this order occur in the Trias of Germany, 

 Scotland, North America, and India. Th^ey are all extremely generalised 

 forms, belonging to the sub-orders Parasuchia and Fseudosuchia, and possess a 

 number of characters in common with Dinosaurs, lihynchocephalians, and 

 Lacertilians. Many of the Parasuchia, in fact, are referable to Dinosaurs with 

 as much propriety as to Crocodilians. 



True crocodiles, represented by the Mesoswhia, appear rather suddenly in 

 the Lias of England, France, and Germany, and persist essentially unmodified 

 throughout 'the Jura. In none of them is the secondary palate developed 

 back of the posterior margin of the palatines, there being no outgrowths from 

 the pterygoids, and the vertebrae are amphicoelous, or at the most amphi- 

 platyan. Their universal occurrence in marine deposits, the nature of their 

 fossilised stomach contents and coprolites, and their general Organisation, 

 prove them to have been adapted for an exclusively aquatic existence. The 

 earliest forms are all of the longirosträte variety, and it is not until the Upper 

 Jura that short- and broad-headed genera with small supratemporal vacuities 

 are initiated. Owen has suggested that the appearance of the latter is corre- 

 lated with the incoming of warm-blooded prey, and points to the associaticn 

 of dwarf crocodiles in the Purbeck with small mammalian remains. 



Toward the close of the Jura changes in external conditions seem to have 

 created a new environment, for in the Purbeckian and Wealden remains of 

 crocodiles are accompanied for the first time by fresh-water and terrestrial 

 forms, and the indications suggest a fluviatile habitat. In the Wealden are 



