DINOSAURIA. 



197 



bears an ascending process apposed to the anterior face of the 

 lower end of the tibia, exactly as in young Ratite birds. 



Sub-Order 1. Theropoda. 



All the earliest known Dinosaurs, of Triassic age, are carni- 

 vorous, with cutting teeth implanted in distinct sockets. Their 

 bones are of comparatively delicate construction, the vertebrae 



ptn 



FIG. 118. 



Anchisaurus colurus; skull from the superior (A), lateral (B), and occipital (C) 

 aspects, one-half nat. size. Triashic; Connecticut, a, external narial 

 opening; b, antorbital vacuity; bp., basipterygoid process of basisphenoid ; 

 c, lateral temporal vacuity; d, supratemporal vacuity ; /, frontal; j, jugal ; n, 

 nasal; o, orbit; oc., occipital condyle; p, parietal; p', paroccipital process ; 

 ;/., prefrontal; pm., premaxilla; q, quadrate. (After Marsh.) 



and limb-bones being hollow. The fore limbs are small, loco- 

 motion having doubtless been mainly bipedal, and the hind feet 

 are digitigrade. The digits are provided with prehensile claws. 

 The brain-case is incompletely ossified, and there is a large 

 antorbital vacuity in the skull. There is no predentary 

 bone. The sternum is unossified. The pelvic acetabulum is 



