426 



DIXOSAURIA 



the length of that of the hind-limbs, so that these creatures, 

 which were undoubtedly quadrupedal, must have had a very 

 peculiar gait, standing with the head, neck, and shoulders much 

 lower than, the arched back and pelvic region. The ulna has a 

 strong olecranon ; the hand has four functional fingers. The pre- 

 acetabular portion of the ilium is much elongated ; the pre-pubic 

 branch stands horizontally, while the post-pubis is closely adpressed 

 to the ischium. The astragalus is fused with the tibia, the 

 calcaneum with the fibula. The foot has only three short toes, 

 protected, like the fingers, by hoofs. The dorsal dermal armature 



FIG. 100. Skeleton and dermal armour of Stegosaurus ungulatus, x -3$. (After Marsh.) 



consists of very high, crest-like plates. S. ungulatus of North 

 America has a computed length of 28 feet, with the hind-limbs 

 about 7 feet long. This creature was nearly 10 feet high, when 

 measured from the ground to the tips of the dermal crests on the 

 middle of the back. These bony, laterally compressed plates are 

 themselves nearly 3 feet high, and are replaced, on the hinder 

 portion of the tail, by several pairs of pointed spikes about 

 2 feet in length. 



Sub-Order 2. Ornithopoda. The hind-limbs are distinctly 

 digitigrade, usually with only three functional toes, protected by 

 claws. The long bones are hollow. Femur with a long fourth 

 trochanter. Without dermal armour-plates. 



Camptosaurus. Several species, up to 10 feet in length, from 



