240 



REPTILIA 



CLASS III 



Trachodon, Leidy (Hadrosaurus, Thespesius, Leicly ; Didonius, Cope), (Figs. 

 343-345). Skull elongated, depressed, with broad, beak-like snout, very lar.o-e 



PllL2C 



Fig. 343. 



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

 aspects of skull, i/l2- ^i Orbit; ang, Angular; art. Articular; fr. Frontal; ju, Jugal ; la, Lachrymal; mx, 

 Maxilla ; N, Antorbital vacuity ; na, Nasal ; pa, Parietal ; p}nx, Premaxilla ; prcl, Predentary ; prf, Prefrontal ; 

 %itf, Postfrontal ; qu, Quadrate; quj, Quadrato-jugal ; 5, Lateral temporal vacuity; S', Supratemporal vacuity; 

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



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



Fig. 344. 



Trachodon foulli, Leidy. Upper Cretaceous ; 

 New Jersey. Inner (A), outer (£), and (C), lateral 

 aspects of mandibular tooth, somewhat worn, i/i 

 (after Leidy). 



mmm 



t^iMm^^-'-'^'' 





.m 



Fig. 345. 



Traclioclon breviceps, Marsh sp. Upper Cretaceous ; 

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

 functional and successional teeth of dentary, 1/4 

 (after :\Iarsh). 



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

 groove opening inwardly, the successional teeth forming several tectiform 



