viii INTRODUCTION. 



With regard to the sources from whence I have derived the materials for the 

 present Monograph, I have first to acknowledge the value of Mr. S. V. Wood's 

 extensive series of Entomostraca from the Crag of Suffolk (chiefly from Sutton), which 

 he most liberally confided to my care for description. 



Mr. F. Edwards also kindly placed his numerous specimens from Barton, High 

 Cliff, Col well, and Bracklesham in my hands; Mr. H. C. Sorby supplied the Brid- 

 lington specimens ; and I have the pleasure of noticing in the Monograph my debts to 

 Mr. Brown, Mr. Pickering, Mr. Harris, Mr. Wetherell, Mr. Parker, Mr. Prestwich, 

 and other friends for like assistance. 



The London Clay specimens were chiefly collected by Mr. J. Purdue from the 

 Copenhagen Fields. 



To Mr. Morris and Mr. Salter I am especially obliged for the opportunity of 

 examining an extensive series of " Cypris-shales " from the Hempstead and the 

 Osborne Series of the Isle of Wight, chiefly collected by the officers of the Geological 

 Survey, and some by Mr. Morris himself. Previously I possessed but a limited supply 

 of these shales ; but the new materials, though too late for illustration in the plates of 

 this Monograph, enabled me to determine one additional species, and to add to my 

 descriptions of some others. 



The specimens at my command from several of the localities referred to in the 

 Monograph represent tolerably well the Entomostracan fauna of the deposits yielding 

 them. The following may be considered as more or less fully illustrated, viz. the 

 Newbury peat-beds (indifferently), the Cambridgeshire peat-marl, the Copford fresh- 

 water deposits (indifferently), the Pleistocene beds at Grays, Clacton (indifferently), and 

 Wear Farm, the Crag of Sutton, the Upper Eocene shales of Hempstead Cliff, the 

 Middle Eocene beds at Colwell, Barton, and Bracklesham, and the London Clay at 

 Copenhagen Fields. 



The distribution of the Tertiary Ostracoda and their proportional occurrence are 

 generally indicated in the text ; but the synoptical tables of the distribution and 

 relative abundance of the species, given in the Appendix (Tables I, II, III), will, it is 

 hoped, materially assist the student and collector in this respect. 



Frequently a deposit has been too imperfectly worked for a sufficiently good result 

 for the purposes of comparison to have been obtained, — such as at Edwardstone, 

 Alum Bay, East Woodhay, &c. Still the Post-tertiary era and each of the divisions of 

 the Tertiary formation are perhaps, as far as the South East of England is concerned, 

 fully represented by the combined product of the several localities where the different 

 deposits have been met with. 



In indicating the geological series to which the several deposits both in England 

 and on the Continent belong, I have chiefly followed the valuable Table at p. 105, of 

 Lyell's ' Manual of Elementary Geology,' 5th edition. 



