146 Transactions of the Society. 



bone ; the bones of the pelvis and the metatarsals are all eo-ossified", 

 as in existing birds. The premaxillaries each contained three, 

 and the maxillaries had each fifteen, large, powerful, and trenchant 

 teeth, clearly indicating (as in our own Oolitic Megalosaurus) the 

 ferocious character of the animal. 



Of the other carnivorous Dinosaurs of the American Jurassic, 

 three forms, Allosaurus, Crcosaurus, and Labrosaurus, are specially 

 worthy of notice. They were the natural enemies of the gigantic 

 herbivorous forms that were so abundant in the same period. All 

 had powerful jaws, sharp, cutting teeth, and a flexible neck. The 

 fore-limbs were quite small, and the feet (manus and pes) were 

 armed with strong claws for seizing their living prey. The hind- 

 limbs were large and strong, and the animals probably used these 

 alone either in running or leaping, or for ordinary locomotion. 



The herbivorous Dinosaurs comprising the Sauropoda are the 

 most primitive and gigantic forms of the group. Atlantosaurus^ 

 is only known from imperfect remains ; but the pelvic bones and 

 femur of A. immanis give an idea of its gigantic size. The femur 

 is over 6 ft. in length, and this, with the other portions of the 

 skeleton, indicate (says Marsh) an animal about 70 or 80 ft. in 

 length ! 



Brontosaurus is known from nearly an entire skeleton, which 

 measured more than 60 ft. in length. The head is remarkably 

 small, probably smaller in proportion to the body than in any 

 other known reptile. The neck is long and flexible, the body 

 short, the tail much elongated. There are about thirteen cervical 

 vertebra?, with a very small neural canal and no neural spines. 

 The hatchet-shaped ribs are fused with the anterior cervicals but 

 free on those behind. Its skeleton is distinguished among Dino- 

 saurs by the peculiar lightness of its vertebral column, the cervical, 

 dorsal, and sacral vertebrae, all having very large cavities in their 

 centra ; the first three caudals, also, are lightened by excavations 

 in their sides. 



An animal fully equal in size to Brontosaurus, named Cetio- 

 saurus, has been obtained from the Oxford Clay of Peterborough, 

 and, although imperfect, the skeleton shows it to have been as 

 large as the American form.* 



The Sauropodous Dinosaurs, of which Cetiosaurus and Diplodo- 

 cus are examples, are the largest known four-footed animals. Their 

 weight must have been so great that it is difficult to believe they 

 were active on the land. Their remains are often found in marine 

 deposits, and Prof. E. D. Cope has suggested that, like the extinct 

 sea-cow {Bhytina), they may have lived on the sea-shore browsing; 



* This specimen may be seen exhibited in the Reptilian Gallery of the Geo- 

 logical Department, British Museum of Natural Hi.-tory, Cromwell Road, haviug- 

 been lately set up by the present Keeper. Dr. Arthur Smith Woodward, F.R.S. The= 

 specimen was obtained by A. N. Leeds, Esq., F.G.S., Eyebury, mar Peterborough. 



