vl INTRODUCTION. 
and recorded, and so many generalizations have to be made, entirely to avoid 
blunders. In many cases it is impossible to procure the material necessary to 
verify the statements of others, but in all doubtful points I have endeavoured to do 
so. Much work remains to be done before the families of the Passeres, the Columbe, 
the Psittaci, and a few other suborders can be satisfactorily diagnosed ; but in the 
meantime I have ventured to publish my imperfect schemes in the hope that they 
may induce others to help to fill up the gaps and correct the mistakes, and if 
possible decide which of the two schemes presented for criticism appears to be 
the most natural. 


