3i6 



CLASSIFICATION OF VERTEBRATES. 



Diplodocus, from the upper Jurassic of Wyoming and Colorado, are the 

 best-known forms, one species of Camarasaurus measuring 115 feet in 

 length. Only fragments are known of the European species. 



SUB-ORDER 2. THEROPODA. 



Moderate-sized digitigrade carnivorous dinosaurs with short fore limbs 

 and long tail ; vertebra; massive or hollow, the anterior ones opistho- or 

 amphiccele ; a large preorbital fossa, nares large, lateral; premaxilla 

 toothed, teeth pointed, dagger shaped, with serrate margins, seated in 

 alveoli ; no postpubis ; bones of extremities hollow ; femur with inner 

 trochanter, digits 5 or 3, with claws. The species range in size from that 

 of a cat (Compsognathus} to that of an elephant (Megalosaurus}. In 

 Europe the sub-order was restricted to the triassic and Jurassic ; in Amer- 

 ica from the triassic to the upper cretaceous. Allosaurus, Megalosaurus 

 (Lcelaps)^ and Ceratosaurus are the best-known American genera. Prob- 

 ably some, at least, of the famous footprints of the triassic of the Con- 

 necticut Valley and New Jersey were made by forms belonging to this 

 sub-order. 



SUB-ORDER 3. ORTHOPODA. 



Large herbivorous dinosaurs with solid vertebrae ; preorbital fossa 

 small or absent; nares large, anterior; premaxilla toothless, or with teeth 

 behind, lower jaw with an anterior toothless predental bone ; teeth flattened, 

 the edges serrate. Fore legs usually very short, the hind feet with three 

 (rarely four) functional toes. The sub-order is divided into three sections : 



A. STEGOSAURIA. 

 Plantigrade orthopods with a 

 well-developed exoskeleton ; 

 the bones massive, the verte- 

 brae flat or amphiccelian. 

 Prepubes not united in front, 

 postpubes slender and par- 

 allel to ischium. Terminal 

 phalanges hoof-like. Best 

 known are Scelidosaurus, 

 from the lower lias of Eng- 

 land, and Hypsirhophus 

 (Stegosaurus), from the Ju- 

 rassic of the western U. S. 



B. CERATOPSIA. Plan- 

 tigrade orthopods with well-developed dermal skeleton, sometimes forming 

 a complete cuirass. Bones massive ; vertebrae flat : skull with pointed pro- 

 cesses on the frontals and with the parietals broadly expanded posteriorly. 

 A 'rostral bone' in front of the premaxilla. No postpubis; prepubes 

 distally expanded and united by symphysis. Femur without third tro- 



FIG. 310. Skull of Agatha umas, after Marsh. 

 e, eye ; h, horn ; /, predentary ; ;-, rostrum. 



