382 CROCODILIA. 



Order 2. PSEUDOSUCHTA.* 



Extinct Triassic (Keuper) Crocodilia found in Germany, Scotland, and 

 Xew Mexico. With short premaxillae, anterior and laterally-placed 

 nostrils, large orbits, teeth in anterior part of jaw only, two rows of bony 

 plates on the back. Aetosaurus Fraas, Or nithosuchus Newton, and Erpeto- 

 saurus Newton from the Elgin Sandstone, Typothorax Cope, New Mexico. 



Order 3. EUSUCHIA. 

 (Mesdsuchia and Eusuchia of Huxley, Crocodiles proper.) 



With biconcave (in extinct forms) or procoelous vertebrae, short pre- 

 maxillaries enclosing the nostril which is single and placed at the end of the 

 snout ; internal nares placed far back behind the palatines (Fig. 204), in 

 recent forms in the hinder part of the pterygoids (Fig. 205). In the pre- 

 cretaceous forms and in some of the cretaceous, the median eustachian 

 canal is enclosed in bone, but the lateral canals are represented only by 

 grooves ; parietals unpaired, clavicles absent, pubis not entering into the 

 acetabulum. Anterior feet with five, posterior with four toes and traces 

 of a fifth. When the snout is long, its elongation is due to the maxillaries. 

 They are known since Lower Jurassic times. The living forms which 

 with the exception of one species of Alligator found in China are inter- 

 tropical, are grouped in two families and six genera. 



Fam. 1. Teleosauridae. Snout long and slender, vertebrae biconcave, 

 internal nares at the hinder end of the palatines, anterior limbs half the 

 length of the posterior, nasals separated by a wide interval from the small 

 premaxillaries, a small preorbital foramen, prefrontal small, lacrymal 

 large. Two rows of large dorsal and several rows of smaller ventral bony 

 plates. Lias and Oolite of Europe, marine. Mystriosaurus Kaup., Pela- 

 gosaurus Brown, Steneosaurus Geoffrey, Teleosaurus Geoff. 



Fam. 2. Metriorhynchidae. Vertebrae biconcave, snout fairly long, 

 nasals broad, internal nares at hind end of palatine, prefrontals large, 

 lacrymal small, eyes with bony ring in sclerotic, skin without bony plates, 

 Upper Jurassic, marine. Metriorhynchus v. Meyer, Geosaurus Cuv. etc. 



Fam. 3. Maerorhynehidae. Vertebrae biconcave, snout long and 

 slender, nasals narrow and long, internal nares at the hind end of the pala- 

 tine, dermal armour of dorsal and ventral plates, in the fresh-water de- 

 posits of the Purbeck, Wealden and Greensand of Europe. Macroryhnchus 

 Dunker, Petrosuchus Owen. 



Fam. 4. Atoposauridae. Body small, lizard-like ; snout short, rounded ; 

 vertebrae biconcave ; without ventral dermal armour ; Upper Oolite of 

 France ; marine. Atoposaurus v. Meyer, Alligatorium Jour dan, Alli- 

 gatorellus Jourd. 



Fam. 5. Goniopholidae. Vertebrae biconcave ; snout moderately 

 elongated ; choanae far back between the palatines and pterygoids ; 

 with dorsal bony plates. Fossil in Purbeck, Wealden of Europe and 

 Upper Jurassic of N. Amer. Goniopholis Owen, Nannosuchus Ow., Therio- 

 suchus Ow., Bernissartia Dollo. 



Fam. 6. Gavialidae. Vertebrae procoelous, teeth subequal, snout long 

 and slender, nasals widely separate from nasal aperture, internal nares 



* Fraas, "Aetosaurus ferratus," Wurttemb. naturw. Jahreshefte, 23, 

 1867. Newton E. T. Phil Trans., 185, 1894. 



