xiv ODONTORNITHES. 



The material is abundant for a series of monographs on the marvel- 

 lous extinct vertebrates of this country, and the results already attained are 

 full of promise for the future. A somewhat careful estimate makes the 

 number of new species of extinct vertebrates, collected since 1868, and 

 now in the Yale College Museum, about 1,000. Nearly 300 of these have 

 already been described by the writer, and some have been noticed or 

 described by other authors, but at least one-half remain to be investigated. 



Among the new groups brought to light by these researches, and 

 already made known by descriptions of their principal characters, are the 

 following, which will be fully described in subsequent volumes of the 

 present series. 



The first Pterodactyles, or flying reptiles, discovered in this country, 

 were found by the writer in the same geological horizon with the Odontorni- 

 thes, described in the present memoir. These were of enormous size, some 

 having a spread of wings of nearly twenty-five feet ; but they were espe- 

 cially remarkable on account of having no teeth, and hence resembling 

 recent birds. They form a new order, Pferanodontia, from the type genus 

 Pteranodon. Of this group, remains of more than six hundred individuals 

 are now in the Yale College Museum — ample material to illustrate every 

 important point in their osteology. 



With these fossils, were found also great numbers of Mosasauroid 

 reptiles, a group which, although rare in Europe, attained an enormous 

 development in this country, both in numbers and variety of forms. 

 Remains of more than fourteen hundred individuals, belonging to this 

 order, were secured during the explorations of the last ten years, and are 

 now in the Museum of Yale College. 



The most interesting discoveries made in the Jurassic formation were 

 the gigantic reptiles belonging to the new sub-order Sauropoda, including 

 by far the largest land animals yet discovered. Another remarkable 

 group of large reptiles found in the same formation were the Stegosauria. 

 Other Dinosaurs from the same horizon, the " Atlantosaurus beds," 

 show that this was the dominant form of vertebrate life in that age, and 

 many hundred specimens of these reptiles are now in the Yale Museum- 



