2(3 PREFACE. 
plates, mostly engraved and colored in that city 
— a labor of good will, which has required 
time and patience that no one except a gen- 
tleman thoroughly imbued with a desire to pro- 
mote the cause of Natural History could have 
performed, and without which, the work could 
not have appeared. 
To the venerable Alexander Lawson, the en- 
graver of the Birds of Wilson, the author's 
acknowledgments are due for his efforts to ren- 
der the illustrations, mostly engraved by him, 
worthy of his own reputation as an accurate 
zoological engraver, and worthy of the confidence 
of naturalists. 
The author is gratified in announcing that the 
anatomical details of the species, together with 
the dissections and drawings, are exclusively due 
to the labors of Joseph Leidy, M. D., of Philadel- 
phia. They constitute the most novel and impor- 
tant accessions to science contained in the work, 
and are an honorable evidence of a skill and 
industry which entitle him to a high rank among 
philosophical zoologists. 
Before commencing the descriptive part of the 
work, the author has found it convenient to enter 
