12 PREFACE. 



It gives me much pleasure to acknowledge my great obligations 

 to Dr. Wharton, the Rev. Dr. Walker, and Mr. J. E. Harting for 

 very kindly furnishing me with their Lists of Hampstead Species, 

 which derive a value both from not having been previously pub- 

 lished and from the scientific position and long experience of their 

 Authors. 



J. L. L. 



City of London College, 

 August, 1889. 



