1896.] of Birds and Dinosaurs. 205 



"pubis" of Birds). The right and left pubes form no symphysis 

 but remain widely asunder. 



A. Stegosauri: Plantigrade. Tarsals and metatarsals free. 

 Sometimes three-toed. Forelimbs massive, not much shortened. 

 — With a dermal armour. 



Scelidosaurus from the Lias to the Chalk, in England. 

 Stegosaarus from the Jurassic of North America. 



B. Ornithopoda. Forelimbs much shorter than the hindlimbs, 

 but stout and pentadactyle. Hindlimbs elongated ; digitigrade. 

 Femur with a fourth trochanter. 



Camptosaurus and Laosaurus from the Upper Jurassic of North 

 America. Tarsals and metatarsals free. Fifth toe lost, first not 

 functional ; number of phalanges of the first to fourth toes 2, 

 3, 4, 5. 



Hypsilophodon, from the English Wealden. Metacarpals 

 short, the fifth vestigial ; the four fingers with 2, 3, 4, 2 phalanges ; 

 first and fourth fingers much reduced. Astragalus and calcaneus 

 separate. Metatarsals elongated, free ; fifth vestigial. Toes with 

 2, 3, 4, 5 phalanges. 



Iguanodon. Wealden of Europe. Astragalus, calcaneus and 

 distal tarsals free. Metatarsals free, first styliform, fifth lost. 

 Toes with 3, 4, 5 phalanges. 



Hadrosaurus and Diclonius, from the Upper Cretaceous of 

 North America ; allied forms in Europe. The most differentiated 

 of all Ornithopoda, as shown by its bill. 



Omithomimus. Upper Cretaceous of Colorado. The systematic 

 position of this creature must remain doubtful, only the fore- and 

 hindlimbs, without their girdles, being known. The metatarsals, 

 of which only the second, third and fourth are developed, are much 

 elongated ; the third is, with its proximal half, pushed back between 

 the second and fourth, exactly as in Birds. The astragalus has an 

 ascending process and is fused with the tibia. The fibula is very 

 slender. 



IV. Ceratopsia. Marsh. Pubis simple, with symphysis. 

 Femur without inner or fourth trochanter. Forelimbs very little 

 shorter than the hindlimbs. Pentadactyle, quadrupedous. — Man- 

 dible with a toothless " predental " and premaxilla, likewise with a 

 toothless separate element, the so-called os rostrale. — With dermal 

 armour. Skull " horned." 



The Ceratopsia consequently combine characters of the Sauro- 

 poda and Orthopoda ; their occurrence in the Cretaceous for- 

 mations of Europe and of North America, justifies us in treating 

 them as a separate group of the Dinosauri. 



Ceratops and Triceratops from Europe and North America. 



It is easy to select a considerable number of characters amongst 

 the various Dinosaurs, which also reoccur in Birds, and some of 



