INTRODUCTION. 



The present volume continues the list of the known species of Passeri- 

 formes down to the end of the CertJiiidce. Owing to the increasing 

 pressure of official work, it has taken longer to prepare than I anticipated, 

 the number of species described since the ' Catalogue of Birds ' being 

 truly remarkable, and requiring much time and labour for their 

 enumeration. 



In my efforts to accomplish this object, I have been assisted, as before, 

 by a number of my brother Ornithologists, to whom the proofs of the 

 work have been submitted. I am especially indebted to the under- 

 mentioned Naturalists for material help in this respect ; and the reviews 

 of the genus Lanius by Mr. Ogilvie Grant, and of the Paridce by 

 Dr. Bianchi have lightened my labours considerably. The monograph of 

 the Paridce, Sittidce, and Gerthiidce, published by Dr. Hellmayr in the 

 ' Tierreich,' appeared after the present volume was in type, so that I have 

 not been able to avail myself of his conscientious work to the extent 

 which I should have wished. I have again pleasure in acknowledging 

 the assistance rendered by my chief attendant, Mr. Charles Chubb, 

 especially in the preparation of the Index. 



The following gentlemen, who have revised the proofs of the present 

 volume, deserve my warm thanks for their assistance : — 



England. — Dr. P. L. Sclater, Mr. Howard Saunders, Hon. "Walter 

 Eothschild, D.Sc, M.P., Mr. Ernst Hartert, Mr. W. E. Ogilvie 

 Grant, Dr. C. W. Andrews, and Mr. W. P. Pycraft. 



France. — Prof. Dr. Oustalet. 



