204 DINOSAURS OF NORTH AMERICA. 



Another important character, seen also in the genus Ceratosaurus of 

 the Jurassic, is found in the pelvis, the bones of which are firmly coossi- 

 fied with each other and with the sacrum. 



ORNITHOMIMUS. 



The most marked characters of the genus Ornithomimus already 

 determined are manifest in the limbs and feet, and these have been 

 selected for description in the present article. A typical example is 

 shown on PI. LVIII, figs. 1-4, which is the type specimen, the species 

 being Ornithomimus velox Marsh. 



On the distal part of the tibia represented in fig. 1 the astragalus is 

 seen in place, with a very large ascending process, larger than in any 

 dinosaur hitherto known. The calcaneum is also shown in position, 

 but the slender fibula is absent. This bone was complete, but of little 

 functional value. The tibia and all the larger limb bones were hollow, 

 with thin walls, as indicated in the section, fig. 1, c. 



In fig. 5 the corresponding parts of a young ostrich are shown for 

 comparison. The slender, incomplete fibula is in place beside the tibia. 

 The astragalus with its ascending process, and the distinct calcaneum, 

 are also shown in position. The almost exact correspondence of these 

 different parts in the bird and reptile will be manifest to every anato- 

 mist. 



THE METATARSALS. 



The most striking feature of the foot belonging with the reptilian 

 tibia is shown in the metatarsals represented in fig. 2, A. These are 

 three in number, and are in the same position as in life. They are the 

 three functional metatarsals of the typical Ornithopoda and of birds. 

 The distal ends of these bones correspond in size and relative position 

 in the two groups, but here, in the present specimen, the reptilian 

 features cease, and those of typical birds replace them. In all the 

 reptiles known hitherto, and especially in dinosaurs, the second, third, 

 and fourth metatarsals are prominent in front, at their proximal ends, 

 and the third is usually the largest and strongest. In birds the place 

 of the third is taken above by the second and fourth, the third being 

 crowded backward and very much diminished in size. 



This character is' well shown in fig. 0, which represents the second, 

 third, and fourth metatarsals of a young turkey, with the tarsal bones 

 absent. In the reptilian metatarsals seen in fig. '2 the same arrange- 

 ment is shown, with the tarsals in place. The second and fourth 

 metatarsals have increased much in size iu the upper portion, and 

 meet each other in front. 



The third metatarsal, usually the largest and the most robust 

 throughout, here diminishes in size upward, and takes a subordinate^ 

 posterior position, as in birds. The correspondence between the 

 metatarsals of the bird and reptile are here as strongly marked as in 

 the tibiae and their accompanying elements, above described. 



