240 



REPTILIA 



CLASS III 



Trachodon, Leidy (Hadrosaurus, Thespesius, Leidy ; Diclonius, Cope), (Figs. 

 343-345): Skull elongated, depressed, with broad, beak-like snout, very large 



Piii^t 



Fig. 343. 



Irachodon mirabilis, Leidy. Uppermost Cretaceous (Laramie Formation); Dakota. Superior and lateral 

 aspects of skull, V 12 . A., Orbit; ang, Angular; art, Articular ;• fr, Frontal; ju, Jugal ; la, Lachrymal; mx, 

 Maxilla ; N, Antorbital vacuity ; na, Nasal ; pa, Parietal ; pmx, Premaxilla ; prd, Predentary ; prf, Prefrontal ; 

 pi/, Postfrontal ; qu, Quadrate; quj, Qnadrato-jugal ; S, Lateral temporal vacuity; S', Supratemporal vacuity 

 so, Supraoccipital ; sq, Squamosal (after Cope). 



nostrils, subrectangular orbits, and long and narrow temporal vacuities. Parietal 



A B C 



J: 



Fig. 344. 



Trachodon foulki, Leidy. Upper Cretaceous ; 

 New Jersey, [nner (.1), outer (li), and (C), lateral 

 aspects of mandibular tooth, somewhat worn, Vi 

 (after Leidy). 



Fig. 345. 



Trachodon breviceps, Marsh sp. Upper Cretaceous ; 

 Montana. A, Inner, and B, Superior aspect of 

 functional and successional teeth of dentary, V4 

 (after Marsh). 



very small ; premaxillae edentulous. Teeth closely arranged in an alveolar 

 groove opening inwardly, the successional teeth forming several tectiform 



