PREFACE. Vv 
the author has submitted the manuscript of certain chapters 
to naturalists distinguished by their special knowledge of 
certain groups. The manuscript of the sponges has been 
read by Professor A. Hyatt ; of the worms and Mollusca, by 
Dr. Charles 8. Minot; of the Echinoderms, by Mr. Walter 
Faxon; of the Crustacea, by Mr. J. 8. Kingsley. Proofs of the 
part relating to the fishes have been revised by Professor T.. 
Gill, whose classification as given in his ‘‘ Arrangement of 
the Families of Fishes,” has been closely followed, his defin- 
itions having been adopted often word for word. The man- 
uscript of the Batrachians and Reptiles has been read by 
Professor EH. D. Cope, whose classification, given in his 
“‘Check-List of North American Batrachia and Reptilia,” 
has been adopted. Proofs of the part on birds have been 
read by Dr. Elliott Coues, U.S.A., whose admirable ‘‘ Key 
to the Birds of North America” has been freely used, the 
author’s words having been often adopted without quotation- 
marks. Dr. Coues has also revised the proofs of the pages re- 
ferring to the Mammals. To the friendly aid of all these 
gentlemen the author is deeply indebted. 
As to the illustrations, which have been liberally provided 
by the publishers, a fair proportion are original. The full- 
page engravings of the anatomy of the typical Vertebrates 
have been drawn expressly for this work by Dr. C. 8. Minot ; 
a number have been prepared by Mr. J. 8. Kingsley ; Prof. 
W. K. Brooks has kindly contributed the drawing of the 
nervous system and otocyst of the clam, and a few of the 
sketches are by the author. 
The publishers are indebted to Prof. F. V. Hayden 
for illustrations kindly loaned from the Reports of the U.S. 
Geological Survey of the Territories; a few have been 
loaned by Prof. 8. F. Baird, U.S. Commissioner of Fish and 
Fisheries, and the members of the U.S. Entomological Com- 
mission ; a number have been loaned by the Peabody Acad- 
