690 The Smithsonian Institution 



in South America, but has since been found in Georgia ; and 

 it was from this locality, the only one in the United States 

 then known, that the remains described by Doctor Leidy 

 were obtained. 



The fourth and new genus of American sloths, called the 

 Ereptodon by the author, was established upon a peculiar 

 form of teeth which belonged to an animal of about the size 

 of the Megalonyx, the bones of which were also found in 

 the state of Georgia. 



Doctor Hays, one of the commission to which this memoir 

 was submitted, says in his report, that " the author has not 

 only made valuable additions to our knowledge of an inter- 

 esting tribe of animals, but has also collected and arranged 

 the facts previously known so as to throw new light on the 

 subject, and to render his memoir an important starting-point 

 for future investigators." 



A fourth memoir by Doctor Leidy was published in 1865. 

 It consists of descriptions of remains of reptiles discovered in 

 the Cretaceous formations of the United States, and, like the 

 preceding ones, is one of the quarto series. 



Multitudes of fossils are found in the American Cretaceous 

 formations, though the species appear not to be so numerous 

 as in those of Europe. The mollusks are particularly abun- 

 dant, and among them are a great many species of cham- 

 bered shells. A species of ammonite was found on the Upper 

 Missouri as large as an ordinary fore-wheel of a wagon. 

 Remains of fishes were likewise numerous, sometimes in excel- 

 lent preservation and sometimes fragmentary. The teeth of 

 sharks were especially numerous. Bones of reptiles were also 

 abundant, and their remains form the subject of Doctor 

 Leidy's valuable memoir. 



Nothing further was published in vertebrate paleontology 

 until 1883, when Edward D. Cope's memoir on "The Con- 



