TO THE MEMORY OF THE LATE 



ALEXANDER AGASSIZ, 



TO WHOM THE SOCIETY MADE ITS FIRST AWARD 



OF THE WALKER GRAND PRIZE 



IN RECOGNITION OF HIS 'REVISION OF THE ECHINI. 



AND OF 



ALPHEUS HYATT, 



LATE CURATOR OF THE SOCIETY, 



MY BELOVED MASTER AND FRIEND. WHOSE 



PRINCIPLES OF RESEARCH ARE THE 



KEYNOTE OF THIS MEMOIR. 



