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674 Dritte Sitzung der sechsten Sektion. 



above the ground and gives evidence, especially in its posterior 

 half, of extreme, sinuous flexibility, and armed as it was with 

 sharp-edged plates and spines was the principal weapon of offense 

 and defense against the sanguinary carnivores of that day. 



The great power of the fore limbs is at once evident from 

 the size of the scapular arch, the immense rugosities of the nu- 

 merus and the development of the olecranon process implying a 

 somewhat bent, easily flexed limb excelled only by that of the 

 huge headed dinosaur Triceratops. 



The hind limbs on the contrary while powerful were pillar- 

 like as the straight shaft of the femur and the character of the 

 knee Joint give positive evidence. The fourth trochanter of the 

 femur, so prominent in bipedal dinosaurs, is reduced though the 

 origin of the caudo-femoral muscle is nevertheless distinctly in- 

 dicated. The loss of this trochanter, together with the slight 

 development of the pubic peduncle of the ileum, precludes the 

 possibility of a bipedal gait though doubtless Stegosaurus is de- 

 rived from a bipedal ancestry, quadrupedalism being secondarily 

 acquired as in the Ceratopsia, owing to the immense weight of 

 the creature's armament. 



The vertebrae are unique in the curious upward Prolongation 

 of the neural arch and spine, the transverse processes and zyga- 

 pophyses being borne high upon the latter, thus producing not 

 only a very rigid back when subject to vertical strains but also 

 raising the ribs and so increasing the hing and visceral capacity 

 of the body very materially without adding to its breadth. The 

 whole character of the vertebrae and ribs, the latter being T-shaped 

 in cross-section near their proximal end, thus giving great stiff- 

 ness and a broad bearing surface with the minimum of weight, 

 is a wonderful adaptation for bearing the great dermal plates 

 with which the back was armed. 



The feet are large as though to support the creature's weight 

 on yielding soil, the hand evidently possessing five while the 

 foot bore three well developed digits. The semi-digitigrade feet 

 were doubtless enclosed in a fleshy mass, as in the modern ele- 

 phants, and the external indications of the digits were mainly 

 the hoof-like nails. 



The bod}^ is extremely lank and the hips narrow, the breadth 

 across the deltoid crests of the humeri being the greatest dia- 

 meter of the animal's frame. 



The dentition in common with that of other predentate 

 dinosaurs, except Hypsilophodon, is confined to the rear portion 

 of the jaws, the anterior part of the mouth being entirely tooth- 

 less, very small, and probably ensheathed in a horny cropping 

 beak. 



The dental battery, while of the same general type as that 

 of Camptosaurus or Iguanodon, is very imperfectly developed as 



