ORDER VII CROCODILIA 211 



Sub-Order 2. PSEUDOSUCHIA. Zittel.i 



PremaxiUae reduced; nascds very large. External nares paired, lolaced far 

 forwards ; internal nares separate, in about the middle of the palate. Orbits large, 

 laterally directed. Parietals and frontals paired ; postorbital distinct. Teeth conical, 

 deeply socketed, confined to anterior half of -the jaws. Vertebrae amphiplatyan ; 

 cervical ribs hatchet -shaped, double-headed. Fore-limb slightly shorter than the 

 posterior ; fifth digit of pes reduced, comp>rising but a single phalanx. Dorscd armour 

 consisting of a paired series of oblong scutes. 



Aetosaurus, Fraas (Fig. 312). Body lizard-like, longicaudate, with dorsal 

 and ventral armouring of radially ornamented scutes ; ventral scutes smaller 

 than the dorsal, and almost square. Skull triangular, acuminate in front. 



Fig-. 312. 



Al'tosaurtis ferraUis, Fraas. Upper Keuper ; Heslach, near Stuttgart. Head and anterior portion of trunk, i/.j. 

 A, Orbit ; D, Autorbital vacuity ; N, Narial opening ; S, lateral temporal vacuity (after (). Fraas). 



Antorbital vacuities large, separated from the large external nares by a narrow 

 ascending process of the maxilla. Posterior border of the orbits formed by 

 the postfrontal and postorbital, the inferior border by the jugal. Parietals 

 and frontals similar in form and size. Temporal region imperfectly known. 

 Mandibular rami pierced by a large foramen between the articular and angular. 

 Interclavicle blade-like. Twenty-four complete but slightly crushed in- 

 dividuals are preserved in the Stuttgart Museum, all on a single slab of 

 Stuben Sandstone (Upper Keuper), from Heslach, near Stuttgart. The largest 

 of these has a total length of 86 cm. 



Dyoplax, Fraas. Upper Keuper ; Stuttgart. Typothorax, Cope. Trias ; 

 New Mexico. 



Ornithosuchus, Newton. Skull pointed in front, very similar to Aetosaurus. 

 Orbits large, supratemporal vacuities small, the lateral ones triangular. Teeth 

 slightly recurved, with finely serrated anterior and posterior cutting edges. 

 Vertebral centra elongated, with very stout neural spines. Ilium elongated, 

 ischium slender, pubis long and rod-like. Elgin Trias. 0. woodwardi, Newton. 



Erpetosaurus, Newton. Skull narrow and rounded in front. Orbits sub- 

 elliptical, directed upwards and forwards. Supratemporal vacuities round, the 



^ Literature : 



Fraas, 0., Ueber Dyoplax arenaceus (Wiirtt. Jaliresh. vol. XXIII.), 1867. — Aetosaurus ferratus 

 (ibid. vol. XXXIII. ), 1877.— A^eivtrju, E. T., Reptiles from the Elgin Sandstone (Phil. Trans, vol. 

 CLXXXV.), 1894. 



