PREFACE. 



This monograph owes its existence to the friendly encouragement of Dr. 

 A. Smith Woodward, F.R.S., Keeper, and of Dr. F. A. Bather, F.R.S., Deputy- 

 Keeper of the Geological Department of the British Museum (Natural History), 

 and to these gentlemen I am indebted for the loan of the undescribed Coal Measure 

 fossil insects in their charge, and for much helpful assistance in other ways. 



Others to whom my thanks are due are the Director of the National Museum, 

 Washington, U.S.A. : Dr. F. L. Kitchin, of the Museum of the Geological Survey ; 

 Mr. G. W. Lee, of the Scottish Geological Survey ; Dr. J. A. Clubb, of the Derby 

 and Mayer Museums, Liverpool; Dr. W. E. Hoyle, of the National Museum of 

 Wales, Cardiff ; Prof. W. S. Boulton, of the Birmingham University ; Dr. W. M. 

 Tattersall, of the Manchester Museum, Victoria University ; Mr. L. Gill, M.Sc., of 

 the Hancock Museum, Newcastle ; Mr. H. Y. Simpson, of the Kilmarnock 

 Museum ; and Messrs. Eltringham, S. Priest, W. Egginton, and D. Davies. 



To Mr. W. J. Tutcher I am deeply indebted for his ready assistance in 

 photographing all the various specimens submitted for examination. His remark- 

 able skill has been ahvays at my service, and by means of it I have been able to 

 determine many details of structure which otherwise would have remained 

 obscure. 



I am indebted to the Royal Society for several grants towards the cost of the 

 work. 



H. BOLTOX. 



