PREFACE. V 



ations. Still 1 havC;, in accordance with my original design, given 

 every known specific name, wlietlier synonym or variety, whereby 

 observers may avoid confusion in the nomenclature by not employing 

 the same names for newly-discovered forms. The references now 

 introduced are to works published subsequently to the early editions 

 of this book : for their verification I am indebted to Mr. Kitton 

 of Norwich. 



Twenty-one new Plates have been added to this edition, of which 

 six are engraved by Mr. Tuffen West. In the case of the Diatoms, 

 all the new figures are drawn to one scale, representing a magnifying 

 power of 300 diameters; many of them likewise are drawn from 

 specimens, whilst others are engraved from original drawings kindly 

 lent by Mr. George Norman of Hull, Mr. Eoper of Clapton, and 

 Mr. Brightwell of Normch. 



It now becomes my pleasing duty to acknowledge the kind assist- 

 ance received from the late Professors Gregory of Edinburgh and 

 BxiiLEY of New York; also to tender to Drs. Donivin, Greville, 

 Francis, Wallich, Strethill Wright, and Mr. Gosse, along with 

 the gentlemen before named, my best thanks for their aid and advice 

 during the progress of this laborious undertaking. 



In conclusion, should the object proposed in the reissue of this 

 work be attained, viz. to produce in a single volume a compendium 

 of the present state of knowledge, calculated to promote and facilitate 

 the study of the veiy interesting branch of Natural History which 

 forms its subject, and which has occupied much of my leisure time 

 for more than forty years, I shall be fully content. 



ANDREW PRITCHARD. 



Canonbury, London, N. .•■- ^ T o "*•**>. 



November 15, 1860. /Cm^ ^^A^ ^ 



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