TABLE OF CONTENTS. 



PREFACE 



INTRODUCTION 



I. THE GENUS PISIDIUM 



II. HISTORY OF THE BRITISH SPECIES 



III. LlST OF INDETERMINATE PAL.EARCTIC FORMS 13 



IV. DESCRIPTIONS OF THE SPECIES RECOGNIZED 16 



1. Pisidium amnicum (M tiller) 10 



"2. astartoides, Sandb 27 



3. casertanum (Poll) 31 



4. nitidum, Jenyns 44 



5. personatum, Malm 53 



6. pusillum (Gmelin) Jenyns 60 



7. iitilium, Held 70 



8. pulchellum, Jenyus 78 



!>. subtruncatum, Malm 84 



10. henslowanum (Shepp.) 93 



11. ,, siipinum, A. Schmidt , 100 



1:?. ,, parvulum, Clessin 105 



13. steenbuchii (Moller) 107 



14. lil/Jeborffii, Olessin Ill 



15. hibernicmn, Westld 116 



16. obtusale (Lam. ?) Jenyus 119 



17. vincentianum, B. B. "Woodw 127 



V. BIBLIOGRAPHY 129 



VI. INDEX 141 



PLATES I-XXX, WITH THEIR EXPLANATIONS. 



TEXT FIGURE. 



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