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A REVISION OF THE BRITISH LEECHES. 
By W. A. HARDING, M.A., F.L.S. 
{From the Zoological Laboratory, Cambridge.) 
(Plates XIII to XV and 16 Text Figures.) 
CONTENTS. 
Introduction ..... 
Diagnostic characters 
Descriptive catalogue 
List of British Hirudinea 
Bibliography. 
Description of Plates 
Introduction. 
Since the appearance of Johnston’s Catalogue of the British Non- 
parasitical Worms in the Collection of the British Museum —a work 
which although not published until 1865 had been completed some ten 
years earlier and consequently embodies observations made more than 
half a century ago—the Hirudinea of the British Islands have been 
largely neglected. Apart from this the interest now being taken in 
leeches by students of their protozoan parasites and the absence of any 
recent work upon this group of our fauna seems sufficient apology for 
the revised descriptive catalogue attempted in the following pages. 
The material upon which these observations are based has been 
collected, as far as the fresh-water species are concerned, for the most 
part in the neighbourhood of Cambridge. Consignments of leeches 
however have been received from other quarters, and in this connection 
my thanks are due, amongst others, to Mr Thomas Edwards for 
specimens of Piscicola from the River Test, in Hampshire; to Dr 
F. W. Gamble for examples of Trocheta from the Withington Sewage 
Works, near Manchester; to Mr Hugh Stowell and Mr C. H. Ball for 
further material from the same source, and to Mr M. R. Pryor for 
special information regarding the occurrence of this species in England 
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