682 The Smithsonian Institution 



Conrad's work contains a list of all the species from the 

 Eocene formations of North America up to its publication, 

 and is intended to facilitate the distribution of duplicate speci- 

 mens, while Marcou listed the Mesozoic and Cenozoic in- 

 vertebrate types in the collections of the National Museum. 



These different series of check -lists have fully answered 

 the purpose intended, in supplying a want long felt by stu- 

 dents of natural history. 



The year 1865 is marked by two important publications: 

 Leidy's " Cretaceous Reptiles," which will be referred to 

 again, and Meek and Hayden's report on the " Paleontol- 

 ogy of the Upper Missouri." 



The latter work is in quarto form, and contains figures and 

 descriptions of the various geological formations of Idaho, 

 Dakota, Nebraska, and portions of Kansas. About three 

 hundred and seventy species of invertebrates, nearly all of 

 which are new, are fully described, and the descriptions are 

 accompanied by remarks on the relations of each species to 

 allied forms from other districts in this country and Europe, 

 both living and fossil — their geological range and geograph- 

 ical distribution. The illustrations consist of about one thou- 

 sand figures, occupying forty-five quarto plates. 



A considerable number of the specimens described and fig- 

 ured were collected by Doctor F. V. Hay den in the several 

 expeditions into the regions of the Upper Missouri and Yel- 

 lowstone, sent by the government under the command of 

 Lieutenant G. K. Warren, of the United States Topographical 

 Engineers, to whose scientific zeal and liberal encouragement 

 science is indebted for much of the material upon which the 

 work is founded. But besides these, a large number were 

 collected by Doctor Hayden himself, previous to his connec- 

 tion with the exploring expeditions of the government. The 

 specific descriptions of the fossils described in this work are 



