PREFATORY NOTE. V 



and Macrorhinus angustirostris ; also to the Zoological Society 

 of London for electros of Gray's "Halicyon richardsi," and of a 

 series of historic figures of the walrus published in the Society's 

 "Proceedings," by the late Dr. Gray, and to the proprietors of 

 " Science Gossip," for electros of the full-length figures of seals. 

 These were received through Dr. Coues, who also furnished the 

 full-length views of Eumetopias stelleri and CaUorhinus ursinus. 

 Mr. Allen desires me to express, in this connection, acknowl- 

 edgments of his indebtedness to Prof. Spencer F. Baird, Secre- 

 tary of the Smithsonian Institution, and to Prof. Alexander 

 Agassiz, Director of the Museum of Comparative Zoology, for 

 the liberality with which they have placed at his service the 

 rich material relating to this group of animals contained in the 

 museums respectively under their charge ; to Prof. Henry A. 

 Ward, of Rochester, N. Y., for the use of much valuable 

 material relating to the Walruses that he would not otherwise 

 have seen ; and to Captain Charles Bryant, late special agent 

 of the United States Treasury Department, for his report, 

 kindly prepared at the author's request, for the present work. 

 Also to Dr. Elliott Cones, Secretary of the Survey, for the use 

 of many of the cuts, for valuable suggestions during the prepa- 

 tion and printing of the monograph, and revision of the proof- 

 sheets. 



F. V. HAYDEN, 



United States Geologist. 



