154 



DINOSATJRIA. 



Suborder THEROPODA. 



Premaxilla completely toothed; nares, when known (fig. 26) 

 terminal, and a large preorbital vacuity ; quadrate elongated, and 

 directed backwards; teeth (fig. 28) simple, laterally compressed, 

 backwardly curved, with serrations on the posterior and frequently 

 on at least a portion of the anterior border, and set in distinct 

 sockets. Yertebrse usually with internal cavities, and frequently 



Fig. 25. 



Allosauras fragilis, Marsh. — Leftside of pelvis; from the Upper Jurassic of 



North America. -^ 



acetabulum ; il, ilium ; is, ischium ; p, pubis. 



(From the ' Amer. Journ.') 

 lateral pits ; zygosphenal articulations present ; cervicals opistho- 

 or amphicoelous, longer or shorter than dorsals, and usually with 

 free ribs ; postcervicals amphicoelous ; sacral arches usually sup- 

 ported by single vertebrae ; in some instances only two sacral 

 vertebra) ; caudals usually with postzygapophyses ; chevrons closed ; 

 rib-facets of middle dorsal vertebrae apparently on the transverse 

 processes. Limb-bones hollow; pectoral limb much shorter than 



