Vi PREFACE. 



This review of the Fossil Plants has the general scope of that on Fossil 

 Fishes given in Vol. I., and includes not only a catalogue of the old and 

 descriptions of the new species, but a sketch of the progress of plant life, 

 so far as it is known, from the most ancient to modern forms. 



A place was assigned to this memoir in the present volume, but it 

 could not have been added to tfie matter now published without making 

 the volume too large for convenience or symmetry with its predecessor, 

 and without carrying its cost considerably beyond the amount appropri- 

 ated for its publication. 



It could not have been preferred in a choice of material without ex- 

 cluding much that is of equal value, and that which had been prepared 

 with the assurance that it should appear in this volume. It was un- 

 avoidable, therefore, that its publication should be deferred. 



2. A memoir by Prof. 0. C. Marsh, on the large Wild Hog, or Peccary 

 {Dicotyles comjjremis), which once roamed through the forests of Ohio, but is 

 now entirely extinct. As was mentioned in the preceding volume, a few 

 disjointed fragments of the bony structure of this interesting animal 

 were the only traces of its existence known before the discovery of twelve 

 nearly complete skeletons in the banks of the Olentangy, at Columbus. 

 It is highly desirable, therefore, that this ample material should be made 

 the basis of a monograph, in which the oldest, largest, and least known 

 species of this peculiarly American type of hogs should not only be re- 

 ihabilitated, but should be brought into relations with its physical sur- 

 roundings and the other animals of the fauna to which it bel,onged. No 

 data have hitherto been known from which the natural history of this 

 animal could be written, but with the special fitness of Prof. Marsh for 

 the duty, and the abundant material that can be placed in his hands, he 

 will prepare a memoir that will become a classic in comparative anatomy, 

 and will add greatly to the interest of our reports. 



3. Prof. Marsh has also consented to review all the relics that have 

 been found of our ancient giant beaver {Castoroules OMoemis), and prepare 

 a more complete and accurate description of it than has yet been writ- 

 ten. It will be remembered that the first traces of this creature were 



